Document

Supplemental Cash Flow Information [Abstract]

Other revenue included in the consolidated statements of income that is not from contracts with customers is approximately 1% of total revenue, and therefore is not presented as a separate line item.

Risk and Insurance Services

Risk and Insurance Services revenue reflects compensation for brokerage and consulting services through commissions and fees. Commission rates and fees vary in amount and can depend upon a number of factors, including the type of insurance or reinsurance coverage provided, the particular insurer or reinsurer selected, and the capacity in which the broker acts and negotiates with clients. For the majority of the insurance and reinsurance brokerage arrangements, advice and services provided which culminate in the placement of an effective policy are considered a single performance obligation. Arrangements with clients may include the placement of a single policy, multiple policies or a combination of policy placements and other services. Consideration related to such "bundled arrangements" is allocated to the individual performance obligations based on their relative fair value. Revenue for policy placement is generally recognized on the policy effective date, at which point control over the services provided by the Company has transferred to the client and the client has accepted the services. The contractual terms for certain fee based brokerage arrangements meet the criteria for revenue recognition over time. For such arrangements, revenue is recognized using output measures, which correspond to the progress toward completing the performance obligation. Fees for non-risk transfer services provided to clients are recognized over time in the period the services are provided, using a proportional performance model, primarily based on input measures. These measures of progress provide a faithful depiction of the progress towards completion of the performance obligation.

Consulting

A significant majority of fee revenues in the Consulting segment is recognized over time.

The following schedule disaggregates components of the Company's revenue:



	Three Months Ended March 31,
	2019
Marsh:
EMEA	$	633
Asia Pacific	165
Latin America	78
Total International	876
U.S./Canada	861
Total Marsh	1,737
Guy Carpenter	663
Subtotal	2,400
Fiduciary interest income	23
Total Risk and Insurance Services	$	2,423

Mercer:
Wealth	$	543
Health	442
Career	170
Total Mercer	1,155
Oliver Wyman	518
Total Consulting	$	1,673

The following schedule provides contract assets and contract liabilities information from contracts with customers.



(In millions)	March 31, 2019		January 1, 2019
Contract Assets	$	198	$	112
Contract Liabilities	$	611	$	545

The Company records accounts receivable when the right to consideration is unconditional, subject only to the passage of time. Contract assets primarily relate to quota share reinsurance brokerage and contingent insurer revenue. The Company does not have the right to bill and collect revenue for quota share brokerage until the underlying policies written by the ceding insurer attach to the treaty. Estimated revenue related to achievement of volume or loss ratio metrics cannot be billed or collected until all related policy placements are completed and the contingency is resolved. The change in contract assets from January 1, 2019 to March 31, 2019 is primarily due to $128 million of additions during the period partly offset by $42 million transferred to accounts receivables, as the rights to bill and collect became unconditional. Contract assets are included in other current assets in the Company's consolidated balance sheet. Contract liabilities primarily relate to the advance consideration received from customers. Contract liabilities are included in current liabilities in the Company's consolidated balance sheet. Revenue recognized in the first three months of 2019 that was included in the contract liability balance at the beginning of the year was $169 million. The amount of revenue recognized in the first three months of 2019 from performance obligations satisfied in previous periods, mainly due to variable consideration from contracts with insurers, quota share business and consulting contracts previously considered constrained was $17 million.

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Fiduciary Assets and Liabilities	3 Months Ended
Fiduciary Assets and Liabilities	Mar. 31, 2019
Fiduciary Assets And Liabilities [Abstract]
Fiduciary Assets and Liabilities	Fiduciary Assets and Liabilities In its capacity as an insurance broker or agent, the Company collects premiums from insureds and, after deducting its commissions, remits the premiums to the respective insurance underwriters. The Company also collects claims or refunds from underwriters on behalf of insureds. Unremitted insurance premiums and claims proceeds are held by the Company in a fiduciary capacity. Risk and Insurance Services revenue includes interest on fiduciary funds of $23 million and $13 million for the three months ended March 31, 2019 and 2018, respectively. The Consulting segment recorded fiduciary interest income of $1 million in each of the three month periods ended March 31, 2019 and 2018, respectively. Since fiduciary assets are not available for corporate use, they are shown in the consolidated balance sheets as an offset to fiduciary liabilities. Net uncollected premiums and claims and the related payables amounted to $9.2 billion at March 31, 2019 and $7.3 billion at December 31, 2018. The Company is not a principal to the contracts under which the right to receive premiums or the right to receive reimbursement of insured losses arises. Accordingly, net uncollected premiums and claims and the related payables are not assets and liabilities of the Company and are not included in the accompanying consolidated balance sheets. In certain instances, the Company advances premiums, refunds or claims to insurance underwriters or insureds prior to collection. These advances are made from corporate funds and are reflected in the accompanying consolidated balance sheets as receivables.

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Per Share Data

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Per Share Data



Basic and Diluted EPS Calculation	Three Months Ended March 31,
(In millions, except per share amounts)	2019		2018
Net income before non-controlling interests	$	727	$	696
Less: Net income attributable to non-controlling interests	11		6
Net income attributable to the Company	$	716	$	690
Basic weighted average common shares outstanding	505		508
Dilutive effect of potentially issuable common shares	6		6
Diluted weighted average common shares outstanding	511		514
Average stock price used to calculate common stock equivalents	$	88.54	$	82.83

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Supplemental Disclosures to the Consolidated Statements of Cash Flows

3 Months Ended

Mar. 31, 2019

Supplemental Disclosures to the Consolidated Statements of Cash Flows

The following schedule provides additional information concerning acquisitions, interest and income taxes paid for the three-month periods ended March 31, 2019 and 2018.



(In millions)	2019			2018
Assets acquired, excluding cash	$	180		$	35
Liabilities assumed	(5		)	(4		)
Contingent/deferred purchase consideration	(35		)	(7		)
Net cash outflow for current year acquisitions	$	140		$	24



(In millions)	2019		2018
Interest paid	$	98	$	80
Income taxes paid, net of refunds	$	131	$	128

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Other Comprehensive Income (Loss)

3 Months Ended

Mar. 31, 2019

Equity [Abstract]

Other Comprehensive Income (Loss)



(In millions)	Unrealized Investment Gains (Losses)		Pension/Post-Retirement Plans Gains (Losses)			Foreign Currency Translation Gains (Losses)			Total Gains (Losses)
Balance as of December 31, 2018	$	—	$	(2,953	)	$	(1,694	)	$	(4,647	)
Other comprehensive (loss) income before reclassifications	—		(59		)	94			35
Amounts reclassified from accumulated other comprehensive income	—		22			—			22
Net current period other comprehensive (loss) income	—		(37		)	94			57
Balance as of March 31, 2019	$	—	$	(2,990	)	$	(1,600	)	$	(4,590	)



(In millions)	Unrealized Investment Gains (Losses)			Pension/Post-Retirement Plans Gains (Losses)			Foreign Currency Translation Gains (Losses)			Total Gains (Losses)
Balance as of December 31, 2017	$	14		$	(2,892	)	$	(1,165	)	$	(4,043	)
Cumulative effect of amended accounting standard	(14		)	—			—			(14		)
Other comprehensive (loss) income before reclassifications	—			(100		)	223			123
Amounts reclassified from accumulated other comprehensive income	—			29			—			29
Net current period other comprehensive (loss) income	—			(71		)	223			152
Balance as of March 31, 2018	$	—		$	(2,963	)	$	(942	)	$	(3,905	)

The components of other comprehensive income (loss) for the three-month period ended March 31, 2019 and 2018 are as follows:



Three Months Ended March 31,	2019									2018
(In millions)	Pre-Tax			Tax (Credit)			Net of Tax			Pre-Tax			Tax (Credit)			Net of Tax
Foreign currency translation adjustments	$	96		$	2		$	94		$	228		$	5		$	223
Pension/post-retirement plans:
Amortization of (gains) losses included in net periodic pension cost:
Prior service credits (a)	(1		)	—			(1		)	(1		)	—			(1		)
Net actuarial losses (a)	26			6			20			37			7			30
Effect of settlement (a)	4			1			3			—			—			—
Subtotal	29			7			22			36			7			29
Foreign currency translation adjustments	(72		)	(13		)	(59		)	(120		)	(20		)	(100		)
Pension/post-retirement plans (loss) gains	(43		)	(6		)	(37		)	(84		)	(13		)	(71		)
Other comprehensive income (loss)	$	53		$	(4	)	$	57		$	144		$	(8	)	$	152
(a) Components of net periodic pension cost are included in other net benefit credits in the consolidated statements of income. Tax on prior service costs and net actuarial losses is included in income tax expense.

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Acquisitions and Dispositions

3 Months Ended

Mar. 31, 2019

Business Combinations [Abstract]

Acquisitions and Dispositions

The Risk and Insurance Services segment completed two acquisitions during the first three months of 2019.


•	February – MMA acquired Bouchard Insurance, Inc., a Florida-based full service agency and Employee Benefits Group, Inc., a Maryland-based independent insurance agency.

The following table presents the preliminary allocation of the acquisition cost to the assets acquired and liabilities assumed during 2019 based on their fair values:



For the Three Months Ended March 31, 2019
(In millions)
Cash	$	142
Estimated fair value of deferred/contingent consideration	35
Total consideration	$	177
Allocation of purchase price:
Cash and cash equivalents	$	2
Accounts receivable, net	5
Property, plant, and equipment	1
Other intangible assets	71
Goodwill	97
Other assets	6
Total assets acquired	182
Current liabilities	5
Other liabilities	—
Total liabilities assumed	5
Net assets acquired	$	177

In January 2019, Marsh increased its equity ownership in Marsh India from 26% to 49%. Marsh India continues to be accounted for under the equity method.

Prior-Year Acquisitions

The Risk and Insurance Services segment completed twelve acquisitions during 2018.


•	February – MMA acquired Highsmith Insurance Agency, a North Carolina-based independent insurance brokerage firm.


•	March – Marsh acquired Hoken Soken, Inc., a Japan-based insurance agency.


•	May – Marsh acquired Mountlodge Limited, a Scotland-based independent insurance broker and Lorant Martínez Salas y Compañía Agente de Seguros y de Fianzas, S.A. de C.V., a Mexico-based multi-line insurance broker.


•	June – MMA acquired Bleakley Insurance Services, a California-based provider of employee benefits solutions; Klein Agency, Inc., a Minnesota-based surety and property/casualty agency; and Insurance Associates, Inc., a Maryland-based independent insurance agency.


•	August – Marsh acquired John L. Wortham & Son, L.P., a Houston-based independent insurance broker.


•	October – MMA acquired Eustis Insurance, Inc., a Louisiana-based insurance agency.


•	November – MMA acquired James P. Murphy & Associates, Inc., a Connecticut-based insurance agency.


•	December – MMA acquired Otis-Magie Insurance Agency, Inc., a Minnesota-based insurance agency, and Marsh acquired Hector Insurance PCC Ltd, a U.K.-based captive management company.

The Consulting segment completed eight acquisitions during 2018.


•	January – Oliver Wyman acquired Draw Ltd., a U.K.-based digital transformation agency.


•	March – Oliver Wyman acquired 8Works Limited, a U.K.-based design thinking consultancy.


•	May – Mercer acquired EverBe SAS, a France-based Workday implementer and advisory firm; and Evolve Intelligence Pty Ltd., an Australia-based talent strategy firm.


•	June – Mercer acquired India Life Capital Private Ltd., an India-based investment advisor.


•	November – Mercer acquired Induslynk Training Services Private Ltd., an India-based talent assessment company, Pavilion Financial Corp., a Canada-based investment services firm and Summit Strategies Inc., a Missouri-based investment consulting firm.

Pro-Forma Information



	Three Months Ended March 31,
(In millions, except per share figures)	2019		2018
Revenue	$	4,080	$	4,098
Net income attributable to the Company	$	717	$	694
Basic net income per share attributable to the Company	$	1.42	$	1.37
Diluted net income per share attributable to the Company	$	1.40	$	1.35

Subsequent Event - Acquisition of JLT

Financing and hedging activities related to the Transaction are discussed in more detail in Notes 11 and 14 of the consolidated financial statements.

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Goodwill and Other Intangibles

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Other Intangibles

Changes in the carrying amount of goodwill are as follows:



March 31,
(In millions)	2019		2018
Balance as of January 1,	$	9,599	$	9,089
Goodwill acquired	97		15
Other adjustments^(a)	43		90
Balance at March 31,	$	9,739	$	9,194

^(a) Primarily reflects the impact of foreign exchange.

The goodwill acquired of $97 million in 2019, all of which is deductible for tax purposes, related to the Risk and Insurance Services segment.

Goodwill allocable to the Company’s reportable segments at March 31, 2019 is as follows: Risk and Insurance Services, $6.9 billion and Consulting, $2.8 billion.

The gross cost and accumulated amortization at March 31, 2019 and December 31, 2018 are as follows:



	March 31, 2019						December 31, 2018
(In millions)	Gross Cost		Accumulated Amortization		Net Carrying Amount		Gross Cost		Accumulated Amortization		Net Carrying Amount
Client Relationships	$	2,046	$	685	$	1,361	$	1,970	$	639	$	1,331
Other ^(a)	267		164		103		259		153		106
Amortized intangibles	$	2,313	$	849	$	1,464	$	2,229	$	792	$	1,437

^(a) Primarily non-compete agreements, trade names and developed technology.

Aggregate amortization expense for the three months ended March 31, 2019 and 2018 was $51 million and $45 million, respectively. The estimated future aggregate amortization expense is as follows:



For the Years Ending December 31,
(In millions)	Estimated Expense
2019 (excludes amortization through March 31, 2019)	$	151
2020	187
2021	174
2022	159
2023	156
Subsequent years	637
	$	1,464

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Fair Value Measurements

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

Fair Value Hierarchy


Level 1.	Assets and liabilities whose values are based on unadjusted quoted prices for identical assets or liabilities in an active market (examples include active exchange-traded equity securities and exchange-traded money market mutual funds).

Assets and liabilities measured using Level 1 inputs include exchange-traded equity securities, exchange-traded mutual funds and money market funds.


Level 2.	Assets and liabilities whose values are based on the following:


a)	Quoted prices for similar assets or liabilities in active markets;


b)	Quoted prices for identical or similar assets or liabilities in non-active markets (examples include corporate and municipal bonds, which trade infrequently);


c)	Pricing models whose inputs are observable for substantially the full term of the asset or liability (examples include most over-the-counter derivatives, including interest rate and currency swaps); and


d)	Pricing models whose inputs are derived principally from or corroborated by observable market data through correlation or other means for substantially the full asset or liability (for example, certain mortgage loans).

Assets and liabilities using Level 2 inputs include treasury locks and an equity security.


Level 3.	Assets and liabilities whose values are based on prices, or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs reflect management’s own assumptions about the assumptions a market participant would use in pricing the asset or liability.

Liabilities measured using Level 3 inputs include liabilities for contingent purchase consideration and the deal contingent foreign exchange contract (the "FX Contract").

Valuation Techniques

Equity Securities, Money Market Funds and Mutual Funds – Level 1

Treasury Locks - Level 2

Contingent Purchase Consideration Liability – Level 3

Foreign Exchange Forward Contract Liabilities - Level 3

The following fair value hierarchy table presents information about the Company’s assets and liabilities measured at fair value on a recurring basis as of March 31, 2019 and December 31, 2018.



	Identical Assets (Level 1)				Observable Inputs (Level 2)				Unobservable Inputs (Level 3)				Total
(In millions)	03/31/19		12/31/18		03/31/19		12/31/18		03/31/19		12/31/18		03/31/19		12/31/18
Assets:
Financial instruments owned:
Exchange traded equity securities^(a)	$	21	$	133	$	—	$	—	$	—	$	—	$	21	$	133
Mutual funds^(a)	145		151		—		—		—		—		145		151
Money market funds^(b)	67		118		—		—		—		—		67		118
Other equity investment^(a)	—		—		8		8		—		—		8		8
Total assets measured at fair value	$	233	$	402	$	8	$	8	$	—	$	—	$	241	$	410
Fiduciary Assets:
U.S. Treasury Bills	$	—	$	20	$	—	$	—	$	—	$	—	$	—	$	20
Money market funds	60		80		—		—		—		—		60		80
Total fiduciary assets measured at fair value	$	60	$	100	$	—	$	—	$	—	$	—	$	60	$	100
Liabilities:
Contingent purchase consideration liability^(c)	$	—	$	—	$	—	$	—	$	171	$	183	$	171	$	183
Acquisition related derivative contracts	—		—		—		116		283		325		283		441
Total liabilities measured at fair value	$	—	$	—	$	—	$	116	$	454	$	508	$	454	$	624

^(a)Included in other assets in the consolidated balance sheets.

^(b) Included in cash and cash equivalents in the consolidated balance sheets.

^(c) Included in accounts payable and accrued liabilities and other liabilities in the consolidated balance sheets.

During the three-month period ended March 31, 2019, there were no assets or liabilities that were transferred between any of the levels.

The table below sets forth a summary of the changes in fair value of the Company’s Level 3 liabilities for the three month periods ended March 31, 2019 and 2018:



	Three Months Ended March 31,
(In millions)	2019			2018
Balance at beginning of period,	$	508		$	189
Additions	11			6
Payments	(35		)	(40		)
Revaluation Impact	11			5
Change in fair value of the FX contract	(42		)	—
Other ^(a)	1			1
Balance at March 31,	$	454		$	161

^(a)Primarily reflects the impact of foreign exchange.

Long-Term Investments

Investments Accounted For Using the Equity Method of Accounting

Investments in Public and Private Companies

The Company has other investments in private insurance and consulting companies with a carrying value of $155 million and $61 million at March 31, 2019 and December 31, 2018, respectively.

Private Equity Investments

Other Investments

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

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Derivatives	3 Months Ended
Derivatives	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives On September 20, 2018, the Company entered into the FX Contract to purchase £5.2 billion at a contracted exchange rate, to hedge the risk of appreciation of the GBP-denominated purchase price of JLT. The settlement of the FX Contract was contingent upon the closing of the JLT Transaction. The all in contract exchange rate included the cost of a liquidity premium (due to the size of the JLT Transaction) and a deal contingent feature, which together increased the exchange rate in the FX Contract to purchase the £5.2 billion by .0343. The FX Contract is measured at fair value and the resulting gain or loss is recorded in the consolidated statements of income. The fair value at March 31, 2019 was based on the all in forward rate, adjusted to exclude the liquidity premium compared to the foreign exchange rate at valuation date. Since all conditions to close had been satisfied at March 31, 2019, no value was assigned to the deal contingency feature. The fair value at December 31, 2018 was determined using the probability distribution approach, comparing the all in forward rate to the foreign exchange rate for possible dates the JLT Transaction could close, discounted to the valuation date and adjusted for the fair value of the deal contingency feature. Determining the fair value of the FX Contract required significant management judgments or estimates about the potential closing dates of the transaction and remaining value of the deal contingency feature. An unrealized gain of $42 million related to the change in fair value during the period from December 31, 2018 to March 31, 2019 was recorded in the consolidated statement of income. This gain resulted from the strengthening of the pound sterling partly offset by the cost of the deal contingency feature. The FX Contract does not qualify for hedge accounting treatment under applicable accounting guidance. The FX Contract was settled on April 1, 2019. A loss of $12 million will be recorded in the second quarter of 2019 related to the settlement of the FX contract. In connection with the JLT Transaction, to hedge the economic risk of changes in future interest rates prior to its issuance of fixed rate debt, in the fourth quarter of 2018 the Company entered into treasury locks related to $2 billion of expected issuances of senior notes in 2019. The fair value at December 31, 2018 is based on the published treasury rate plus forward premium as of December 31, 2018 compared to the all in rate at the inception of the contract. The contracts were not designated as an accounting hedge. The Company recorded an unrealized loss of $116 million related to the change in the fair value of this derivative in the consolidated statement of income for the twelve months ended December 31, 2018. In January 2019, upon issuance of the $5 billion of senior notes, the Company settled the treasury lock derivatives and made a payment to its counter party for $122 million. An additional charge of $6 million was recorded in the first quarter of 2019 related to the settlement of the Treasury lock derivatives. In March 2019, the Company issued €1.1 billion of senior notes related to the JLT Transaction. See Note 14 for additional information related to the Euro senior note issuances. In connection with the senior note issuances, the Company entered into a forward exchange contract to hedge the economic risk of changes in foreign exchange rates from the issuance date to settlement date of the Euro senior notes. This forward exchange contract was settled in March 2019 and the Company recorded a charge of $7.3 million related to the settlement of this contract. Net Investment Hedge The Company has investments in various subsidiaries with Euro functional currencies. As a result, the Company is exposed to the risk of fluctuations between the Euro and U.S. dollar exchange rates. As part of its risk management program to help fund the JLT acquisition, the Company designated the €1.1 billion senior note debt instruments as a net investment hedge of its Euro denominated subsidiaries. The hedge will be re-assessed each quarter to confirm that the designated equity balance at the beginning of each period continues to equal or exceed 80% of the outstanding balance of the Euro debt instrument and that all the critical terms of the hedging instrument and the hedged net investment continue to match. If the Company concludes that the hedge is highly effective, the change in the debt balance related to foreign exchange fluctuations will be recorded in accumulated other comprehensive income (loss) in the consolidated balance sheet. The Company concluded that the hedge was highly effective for the quarter ended March 31, 2019.

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Leases

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Leases

The following chart provides additional information about the Company’s property leases:



For the Three Months Ended March 31,
(In millions)	2019
Lease Cost:
Operating lease cost	$	82
Short-term lease cost	1
Variable lease cost	37
Sublease income	(4		)
Net lease cost	$	116
Other information:
Operating cash outflows from operating leases	$	87
Right of use assets obtained in exchange for new operating lease liabilities	—
Weighted-average remaining lease term – real estate	7.7 years
Weighted-average discount rate – real estate leases	3.12		%

Future minimum lease payments for the Company’s operating leases as of March 31, 2019 are as follows:



Payment Dates	Real Estate Leases
Remainder of 2019	$	262
2020	328
2021	276
2022	257
2023	220
2024	183
Subsequent years	610
Total future lease payments	2,136
Less: Imputed interest	(255		)
Total	$	1,881
Current lease liabilities	$	291
Long-term lease liabilities	1,590
Total lease liabilities	$	1,881

Note: Table excludes obligations for leases with original terms of 12 months or less which have not been recognized as a right to use asset or liability in the consolidated balance sheets.

As of March 31, 2019, the Company had additional operating real estate leases that had not yet commenced of $46 million. These operating leases will commence over the next 15 months.

At December 31, 2018, the aggregate future minimum rental commitments under all non-cancelable operating lease agreements are as follows:



For the Year Ended December 31,	Gross Rental Commitments		Rentals from Subleases		Net Rental Commitments
(In millions of dollars)	Gross Rental Commitments		Rentals from Subleases		Net Rental Commitments
2019	$	361	$	32	$	329
2020	$	340	$	31	$	309
2021	$	277	$	12	$	265
2022	$	252	$	10	$	242
2023	$	214	$	9	$	205
Subsequent years	$	753	$	32	$	721

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Retirement Benefits

3 Months Ended

Mar. 31, 2019

Defined Benefit Plan [Abstract]

Retirement Benefits

The components of the net periodic benefit cost for defined benefit and other post-retirement plans are as follows:



Combined U.S. and significant non-U.S. plans	Pension Benefits						Post-retirement Benefits
For the Three Months Ended March 31,	Pension Benefits						Post-retirement Benefits
(In millions)	2019			2018			2019			2018
Service cost	$	8		$	10		$	—		$	—
Interest cost	119			118			1			1
Expected return on plan assets	(213		)	(221		)	—			—
Amortization of prior service (credit) cost	—			—			(1		)	(1		)
Recognized actuarial loss	26			37			—			—
Net periodic benefit (credit) cost	$	(60	)	$	(56	)	$	—		$	—
Settlement loss	4			—			—			—
Total (credit) cost	$	(56	)	$	(56	)	$	—		$	—



Amounts Recorded in the Consolidated Statement of Income
Combined U.S. and significant non-U.S. plans	Pension Benefits						Post-retirement Benefits
For the Three Months Ended March 31,	Pension Benefits						Post-retirement Benefits
(In millions)	2019			2018			2019		2018
Compensation and benefits expense (Operating income)	$	8		$	10		$	—	$	—
Other net benefit (credits) cost	(64		)	(66		)	—		—
Total (credit) cost	$	(56	)	$	(56	)	$	—	$	—



U.S. Plans only	Pension Benefits						Post-retirement Benefits
For the Three Months Ended March 31,	Pension Benefits						Post-retirement Benefits
(In millions)	2019			2018			2019		2018
Interest cost	60			59			—		—
Expected return on plan assets	(86		)	(89		)	—		—
Recognized actuarial loss	11			13			—		—
Net periodic benefit (credit) cost	$	(15	)	$	(17	)	$	—	$	—



Significant non-U.S. plans only	Pension Benefits						Post-retirement Benefits
For the Three Months Ended March 31,	Pension Benefits						Post-retirement Benefits
(In millions)	2019			2018			2019			2018
Service cost	$	8		$	10		$	—		$	—
Interest cost	59			59			1			1
Expected return on plan assets	(127		)	(132		)	—			—
Amortization of prior service credit	—			—			(1		)	(1		)
Recognized actuarial loss	15			24			—			—
Net periodic benefit (credit) cost	$	(45	)	$	(39	)	$	—		$	—
Settlement loss	4			—			—			—
Total (credit) cost	$	(41	)	$	(39	)	$	—		$	—

The weighted average actuarial assumptions utilized to calculate the net periodic benefit costs for the U.S. and significant non-U.S. defined benefit plans are as follows:



Combined U.S. and significant non-U.S. plans	Pension Benefits				Post-retirement Benefits
Combined U.S. and significant non-U.S. plans	Pension Benefits				Post-retirement Benefits
March 31,	2019		2018		2019		2018
Weighted average assumptions:
Expected return on plan assets	5.74	%	5.83	%	—		—
Discount Rate	3.48	%	3.07	%	3.65	%	3.21	%
Rate of compensation increase	1.74	%	1.73	%	—		—

Defined Contribution Plans

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Debt

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Debt

The Company’s outstanding debt is as follows:



(In millions)	March 31, 2019		December 31, 2018
Short-term:
Commercial paper	$	748	$	—
Current portion of long-term debt	814		314
	1,562		314
Long-term:
Senior notes – 2.35% due 2019	300		300
Senior notes – 2.35% due 2020	499		499
Senior notes – 3.50% due 2020	697		—
Senior notes – 4.80% due 2021	499		499
Senior notes - Floating rate due 2021	298		—
Senior notes – 2.75% due 2022	498		497
Senior notes – 3.30% due 2023	348		348
Senior notes – 4.05% due 2023	249		249
Senior notes – 3.50% due 2024	597		597
Senior notes – 3.875% due 2024	992		—
Senior notes – 3.50% due 2025	497		496
Senior notes – 1.349% due 2026	623		—
Senior notes – 3.75% due 2026	597		596
Senior notes – 4.375% due 2029	1,499		—
Senior notes – 1.979% due 2030	622		—
Senior notes – 5.875% due 2033	298		297
Senior notes – 4.75% due 2039	494		—
Senior notes – 4.35% due 2047	492		492
Senior notes – 4.20% due 2048	592		592
Senior notes – 4.90% due 2049	1,236		—
Mortgage – 5.70% due 2035	355		358
Other	4		4
	12,286		5,824
Less current portion	814		314
	$	11,472	$	5,510

The senior notes in the table above are registered by the Company with the Securities and Exchange Commission and are not guaranteed.

In March 2018, the Company issued $600 million of 4.20% senior notes due 2048. The Company used the net proceeds for general corporate purposes.

Fair Value of Short-term and Long-term Debt



	March 31, 2019				December 31, 2018
(In millions)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Short-term debt	$	1,562	$	1,561	$	314	$	313
Long-term debt	$	11,472	$	11,943	$	5,510	$	5,437

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Restructuring Costs

3 Months Ended

Mar. 31, 2019

Restructuring and Related Activities [Abstract]

Restructuring Costs

In addition to the changes discussed above, the Company incurred $3 million of restructuring costs related to severance and future rent under non-cancelable leases, primarily in Corporate.

Details of the restructuring activity from January 1, 2018 through March 31, 2019, which includes liabilities from actions prior to 2019, are as follows:



(In millions)	Liability at 1/1/18		Amounts Accrued		Cash Paid			Other			Liability at 12/31/18		Amounts Accrued		Cash Paid			Other		Liability at 3/31/19
Severance	$	15	$	137	$	(77	)	$	(2	)	$	73	$	37	$	(37	)	$	—	$	73
Future rent under non-cancelable leases and other costs	50		24		(37		)	2			39		1		(4		)	2		38
Total	$	65	$	161	$	(114	)	$	—		$	112	$	38	$	(41	)	$	2	$	111

JLT Related Restructuring

Following the acquisition of JLT, the Company is completing plans for the integration and restructuring of the combined MMC and JLT operations world-wide.

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Common Stock	3 Months Ended
Common Stock	Mar. 31, 2019
Equity [Abstract]
Common Stock	Common Stock There were no repurchases of the Company's common stock during the first three months of 2019. In November 2016, the Board of Directors of the Company authorized the Company to repurchase up to $2.5 billion in shares of the Company's common stock, which superseded any prior authorizations. As of March 31, 2019, the Company remained authorized to repurchase up to approximately $866 million in shares of its common stock. There is no time limit on the authorization. During the first three months of 2018, the Company repurchased approximately 3.0 million shares of its common stock for consideration of $250 million. The Company issued approximately 3.2 million and 2.3 million shares related to stock compensation and employee stock purchase plans during the first three months of 2019 and 2018, respectively.

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Claims, Lawsuits And Other Contingencies	3 Months Ended
Claims, Lawsuits And Other Contingencies	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Claims, Lawsuits, and Other Contingencies	Claims, Lawsuits and Other Contingencies Litigation Matters The Company and its subsidiaries are subject to a significant number of claims, lawsuits and proceedings in the ordinary course of business. Such claims and lawsuits consist principally of alleged errors and omissions in connection with the performance of professional services, including the placement of insurance, the provision of actuarial services for corporate and public sector clients, the provision of investment advice and investment management services to pension plans, the provision of advice relating to pension buy-out transactions and the provision of consulting services relating to the drafting and interpretation of trust deeds and other documentation governing pension plans. These claims may seek damages, including punitive and treble damages, in amounts that could be significant. In establishing liabilities for errors and omissions claims in accordance with FASB guidance on Contingencies - Loss Contingencies, the Company uses case level reviews by inside and outside counsel, and internal actuarial analysis by Oliver Wyman Group, a subsidiary of the Company, and other methods to estimate potential losses. A liability is established when a loss is both probable and reasonably estimable. The liability is reviewed quarterly and adjusted as developments warrant. In many cases, the Company has not recorded a liability, other than for legal fees to defend the claim, because we are unable, at the present time, to make a determination that a loss is both probable and reasonably estimable. To the extent that expected losses exceed our deductible in any policy year, the Company also records an asset for the amount that we expect to recover under any available third-party insurance programs. The Company has varying levels of third-party insurance coverage, with policy limits and coverage terms varying significantly by policy year. Governmental Inquiries and Enforcement Matters Our activities are regulated under the laws of the United States and its various states, the European Union and its member states, and the other jurisdictions in which the Company operates. Risk and Insurance Services Segment In April 2017, the Financial Conduct Authority in the United Kingdom (the "FCA") commenced a civil competition investigation into the aviation insurance and reinsurance sector. In connection with that investigation, the FCA carried out an on-site inspection at the London office of Marsh Limited, our Marsh and Guy Carpenter operating subsidiary in the United Kingdom. The FCA indicated that it had reasonable grounds for suspecting that Marsh Limited and other participants in the market have been sharing competitively sensitive information within the aviation insurance and reinsurance broking sector. In October 2017, the Company received a notice that the Directorate-General for Competition of the European Commission had commenced a civil investigation of a number of insurance brokers, including Marsh, regarding "the exchange of commercially sensitive information between competitors in relation to aviation and aerospace insurance and reinsurance broking products and services in the European Economic Area ("EEA"), as well as possible coordination between competitors." In light of the action taken by the European Commission, the FCA informed Marsh Limited at the same time that it has discontinued its investigation under U.K. competition law. In May 2018, the FCA advised that it would not be taking any further action with Marsh Limited in connection with this matter. In July 2017, the Directorate-General for Competition of the European Commission together with the Irish Competition and Consumer Protection Commission conducted on-site inspections at the offices of Marsh and other industry participants in Dublin in connection with an investigation regarding the "possible participation in anticompetitive agreements and/or concerted practices contrary to [E.U. competition law] in the market for commercial motor insurance in the Republic of Ireland." In January 2019, the Company received a notice that the Administrative Council for Economic Defense anti-trust agency in Brazil had commenced an administrative proceeding against a number of insurance brokers, including Marsh, and insurers “to investigate an alleged sharing of sensitive commercial and competitive confidential information" in the aviation insurance and reinsurance sector. We are cooperating with these investigations and are conducting our own reviews. At this time, we are unable to predict their likely timing, outcome or ultimate impact. There can be no assurance that the ultimate resolution of these or any related matters will not have a material adverse effect on our consolidated results of operations, financial condition or cash flows. Acquisition of Jardine Lloyd Thompson Group plc On April 1, 2019, the Company completed its previously announced acquisition of all of the outstanding shares of Jardine Lloyd Thompson Group plc, a public company organized under the laws of England and Wales (“JLT”). See Note 8 to the consolidated financial statements for additional information. By virtue of the acquisition of JLT, the Company assumed the legal liabilities and became responsible for JLT’s legal and regulatory exposures as of April 1, 2019. Other Contingencies-Guarantees In connection with its acquisition of U.K.-based Sedgwick Group in 1998, the Company acquired several insurance underwriting businesses that were already in run-off, including River Thames Insurance Company Limited ("River Thames"), which the Company sold in 2001. Sedgwick guaranteed payment of claims on certain policies underwritten through the Institute of London Underwriters (the "ILU") by River Thames. The policies covered by this guarantee were reinsured up to £40 million by a related party of River Thames. Payment of claims under the reinsurance agreement is collateralized by segregated assets held in a trust. As of March 31, 2019, the reinsurance coverage exceeded the best estimate of the projected liability of the policies covered by the guarantee. To the extent River Thames or the reinsurer is unable to meet its obligations under those policies, a claimant may seek to recover from the Company under the guarantee. From 1980 to 1983, the Company owned indirectly the English & American Insurance Company ("E&A"), which was a member of the ILU. The ILU required the Company to guarantee a portion of E&A's obligations. After E&A became insolvent in 1993, the ILU agreed to discharge the guarantee in exchange for the Company's agreement to post an evergreen letter of credit that is available to pay claims by policyholders on certain E&A policies issued through the ILU and incepting between July 3, 1980 and October 6, 1983. Certain claims have been paid under the letter of credit and the Company anticipates that additional claimants may seek to recover against the letter of credit. * * * * The pending proceedings described above and other matters not explicitly described in this Note 17 on Claims, Lawsuits and Other Contingencies may expose the Company or its subsidiaries to liability for significant monetary damages, fines, penalties or other forms of relief. Where a loss is both probable and reasonably estimable, the Company establishes liabilities in accordance with FASB guidance on Contingencies - Loss Contingencies. Except as described above, the Company is not able at this time to provide a reasonable estimate of the range of possible loss attributable to these matters or the impact they may have on the Company's consolidated results of operations, financial position or cash flows. This is primarily because these matters are still developing and involve complex issues subject to inherent uncertainty. Adverse determinations in one or more of these matters could have a material impact on the Company's consolidated results of operations, financial condition or cash flows in a future period.

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Segment Information

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Segment Information

The Company is organized based on the types of services provided. Under this structure, the Company’s segments are:


▪	Risk and Insurance Services, comprising insurance services (Marsh) and reinsurance services (Guy Carpenter); and


▪	Consulting, comprising Mercer and Oliver Wyman Group.

Selected information about the Company’s operating segments for the three-month periods ended March 31, 2019 and 2018 are as follows:



	Three Months Ended March 31,
(In millions)	Revenue				Operating Income (Loss)
2019–
Risk and Insurance Services	$	2,423		^(a)	$	733
Consulting	1,673			^(b)	279
Total Operating Segments	4,096				1,012
Corporate/Eliminations	(25		)		(74		)
Total Consolidated	$	4,071			$	938
2018–
Risk and Insurance Services	$	2,344		^(a)	$	716
Consulting	1,668			^(b)	247
Total Operating Segments	4,012				963
Corporate/Eliminations	(12		)		(55		)
Total Consolidated	$	4,000			$	908

Details of operating segment revenue for the three-month periods ended March 31, 2019 and 2018 are as follows:



	Three Months Ended March 31,
(In millions)	2019			2018
Risk and Insurance Services
Marsh	$	1,753		$	1,703
Guy Carpenter	670			641
Total Risk and Insurance Services	2,423			2,344
Consulting
Mercer	1,155			1,171
Oliver Wyman Group	518			497
Total Consulting	1,673			1,668
Total Operating Segments	4,096			4,012
Corporate/Eliminations	(25		)	(12		)
Total	$	4,071		$	4,000

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New Accounting Guidance	3 Months Ended
New Accounting Guidance	Mar. 31, 2019
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Guidance	New Accounting Guidance New Accounting Pronouncements Effective January 1, 2019: The following new accounting standard was adopted using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of January 1, 2019: Leases In February 2016, the FASB issued new guidance intended to improve financial reporting for leases. Under the new guidance, a lessee is required to recognize assets and liabilities for leases. Consistent with legacy GAAP, the recognition, measurement and presentation of expenses and cash flows arising from a lease by a lessee will depend on the classification of the lease as financing or operating. However, unlike legacy GAAP, which requires that only capital leases are recognized on the balance sheet, the new guidance requires that both operating and financing leases be recognized on the balance sheet. The Company adopted this new standard effective January 1, 2019, using a modified retrospective method, applying the new guidance as of the beginning of the year of adoption, with a cumulative effect of initially applying the guidance recognized as an adjustment to retained earnings at January 1, 2019. Therefore, prior period information has not been restated. The Company has elected the package of practical expedients, which among other things, allows us to carry forward our historical lease classifications. The Company did not elect the hindsight practical expedient in determining lease term and impairment of an entity's ROU assets. On January 1, 2019, the Company recognized a lease liability of $1.9 billion and ROU asset of $1.7 billion, related to real estate operating leases. The ROU asset also reflected reclassification adjustments primarily from other liabilities related to existing deferred rent, unamortized lease incentives and restructuring liabilities of $0.2 billion upon adoption. There was no cumulative-effect adjustment required to be booked to retained earnings upon transition. The adoption of this standard did not have a material impact on our income statement as compared to prior periods. The following new accounting standards were adopted prospectively as of January 1, 2019: Derivatives and Hedging In August 2017, the FASB issued new guidance intended to refine and expand hedge accounting for both financial and commodity risks. The guidance creates more transparency around how economic results are presenting in both the financial statements and the footnotes, as well as making targeted improvements to simplify the application of hedge accounting guidance. The Company adopted this guidance effective January 1, 2019. The adoption of this standard did not have an impact on the Company's financial position or results of operations. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income In February 2018, the FASB issued new guidance that allowed an entity to reclassify the stranded tax effects resulting from TCJA from accumulated other comprehensive income ("AOCI") to retained earnings. The guidance is effective for the period beginning January 1, 2019. The Company elected not to reclassify the stranded income tax effects of the TCJA from AOCI to retained earnings. The adoption of this standard had no impact on the Company's financial position or results of operations. The Company’s accounting policy related to releasing income tax effects from AOCI follows the portfolio approach. New Accounting Pronouncements Effective January 1, 2018: The following new accounting standards were adopted using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of January 1, 2018: Revenue Recognition In May 2014, the FASB issued new accounting guidance related to revenue from contracts with customers. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company adopted the new guidance effective January 1, 2018, using the modified retrospective method, which applies the new guidance beginning with the year of adoption, with the cumulative effect of initially applying the guidance recognized as an adjustment to retained earnings at January 1, 2018. The cumulative effect of adopting the standard, net of tax, on January 1, 2018 resulted in an increase to the opening balance of retained earnings of $364 million, with offsetting increases/decreases to other balance sheet accounts, e.g. accounts receivable, other assets and deferred income taxes. Recognition and Measurement of Financial Instruments In January 2016, the FASB issued new guidance intended to improve the recognition and measurement of financial instruments. The new guidance requires investments in equity securities (except those accounted for under the equity method of accounting, or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income; requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (i.e., securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; eliminates the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; and requires a reporting organization to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk (also referred to as "own credit") when the organization has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. The Company adopted the new accounting guidance effective January 1, 2018, recording a cumulative-effect adjustment increase to retained earnings as of the beginning of the period of adoption of $14 million, reflecting the reclassification of cumulative unrealized gains, net of tax as of December 31, 2017 from accumulated other comprehensive income to retained earnings. Income Tax Consequences of Intra-Entity Transfers In October 2016, the FASB also issued new guidance which requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The new guidance eliminates the exception for an intra-entity transfer of an asset other than inventory. The new guidance is effective for public companies for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. The new guidance must be applied on a modified retrospective basis through a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. The Company adopted the new guidance effective January 1, 2018, recording a cumulative-effect adjustment decrease to retained earnings of approximately $14 million as of the beginning of the period of adoption. New Accounting Pronouncements Not Yet Adopted In August 2018, the FASB issued new guidance that amends required fair value measurement disclosures. The guidance adds new requirements, eliminates some current disclosures and modifies other required disclosures. The new disclosure requirements, along with modifications made to disclosures as a result of the change in requirements for narrative descriptions of measurement uncertainty, must be applied on a prospective basis. The effects of all other amendments included in the guidance must be applied retrospectively for all periods presented. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods therein. Early adoption is permitted. Adoption of this guidance will impact disclosures only and will not have an impact on the Company's financial position or results of operations. In August 2018, the FASB issued new guidance that amends disclosures related to Defined Benefit Plans. The guidance removes disclosures that no longer are considered cost-beneficial, clarifies the specific requirements of certain disclosures, and adds disclosure requirements identified as relevant. The guidance must be applied on a retrospective basis. The guidance is effective for fiscal years ending after December 15, 2020. Early adoption is permitted. Adoption of this guidance will impact disclosures only and will not have an impact on the Company's financial position or results of operations. In January 2017, the FASB issued new guidance to simplify the test for goodwill impairment. The new guidance eliminates the second step in the current two-step goodwill impairment process, under which a goodwill impairment loss is measured by comparing the implied fair value of a reporting unit's goodwill with the carrying amount of that goodwill for that reporting unit. The new guidance requires a one-step impairment test, in which the goodwill impairment charge is based on the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. The guidance should be applied on a prospective basis with the nature of and reason for the change in accounting principle disclosed upon transition. The guidance is effective for annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted. The Company does not expect the adoption of this standard to have a material impact on its financial position or results of operations.

XML 46 R28.htm IDEA: XBRL DOCUMENT

Principles of Consolidation and Other Matters (Policies)

3 Months Ended

Mar. 31, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of Accounting

Cash and Cash Equivalents

Investments

Leases

Income Taxes

The Company reports a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in tax returns.

Fair Value Measurement

Fair Value Hierarchy


Level 1.	Assets and liabilities whose values are based on unadjusted quoted prices for identical assets or liabilities in an active market (examples include active exchange-traded equity securities and exchange-traded money market mutual funds).

Assets and liabilities measured using Level 1 inputs include exchange-traded equity securities, exchange-traded mutual funds and money market funds.


Level 2.	Assets and liabilities whose values are based on the following:


a)	Quoted prices for similar assets or liabilities in active markets;


b)	Quoted prices for identical or similar assets or liabilities in non-active markets (examples include corporate and municipal bonds, which trade infrequently);


c)	Pricing models whose inputs are observable for substantially the full term of the asset or liability (examples include most over-the-counter derivatives, including interest rate and currency swaps); and


d)	Pricing models whose inputs are derived principally from or corroborated by observable market data through correlation or other means for substantially the full asset or liability (for example, certain mortgage loans).

Assets and liabilities using Level 2 inputs include treasury locks and an equity security.


Level 3.	Assets and liabilities whose values are based on prices, or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs reflect management’s own assumptions about the assumptions a market participant would use in pricing the asset or liability.

Liabilities measured using Level 3 inputs include liabilities for contingent purchase consideration and the deal contingent foreign exchange contract (the "FX Contract").

Valuation Techniques

Equity Securities, Money Market Funds and Mutual Funds – Level 1

Treasury Locks - Level 2

Contingent Purchase Consideration Liability – Level 3

Foreign Exchange Forward Contract Liabilities - Level 3

New Accounting Pronouncements

New Accounting Guidance

New Accounting Pronouncements Effective January 1, 2019:

The following new accounting standard was adopted using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of January 1, 2019:

Leases

The following new accounting standards were adopted prospectively as of January 1, 2019:

Derivatives and Hedging

Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income

New Accounting Pronouncements Effective January 1, 2018:

The following new accounting standards were adopted using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of January 1, 2018:

Revenue Recognition

Recognition and Measurement of Financial Instruments

Income Tax Consequences of Intra-Entity Transfers

New Accounting Pronouncements Not Yet Adopted

- Definition

Disclosure of accounting policy for investments in financial assets, including marketable securities (debt and equity securities with readily determinable fair values), investments accounted for under the equity method and cost method, securities borrowed and loaned, and repurchase and resale agreements. For marketable securities, the disclosure may include the entity's accounting treatment for transfers between investment categories and how the fair values for such securities are determined. Also, for all investments, an entity may describe its policy for assessing, recognizing and measuring impairment of the investment.

+ References + Details

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Revenue (Tables)

3 Months Ended

Mar. 31, 2019

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

The following schedule disaggregates components of the Company's revenue:



	Three Months Ended March 31,
	2019
Marsh:
EMEA	$	633
Asia Pacific	165
Latin America	78
Total International	876
U.S./Canada	861
Total Marsh	1,737
Guy Carpenter	663
Subtotal	2,400
Fiduciary interest income	23
Total Risk and Insurance Services	$	2,423

Mercer:
Wealth	$	543
Health	442
Career	170
Total Mercer	1,155
Oliver Wyman	518
Total Consulting	$	1,673

Contract with Customer, Asset and Liability

The following schedule provides contract assets and contract liabilities information from contracts with customers.



(In millions)	March 31, 2019		January 1, 2019
Contract Assets	$	198	$	112
Contract Liabilities	$	611	$	545

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Per Share Data (Tables)

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Diluted EPS Calculation Continuing Operations



Basic and Diluted EPS Calculation	Three Months Ended March 31,
(In millions, except per share amounts)	2019		2018
Net income before non-controlling interests	$	727	$	696
Less: Net income attributable to non-controlling interests	11		6
Net income attributable to the Company	$	716	$	690
Basic weighted average common shares outstanding	505		508
Dilutive effect of potentially issuable common shares	6		6
Diluted weighted average common shares outstanding	511		514
Average stock price used to calculate common stock equivalents	$	88.54	$	82.83

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Supplemental Disclosures to the Consolidated Statements of Cash Flows (Tables)

3 Months Ended

Mar. 31, 2019

Supplemental Cash Flow Information [Abstract]

Additional Information Concerning Acquisitions, Interest and Income Taxes Paid

The following schedule provides additional information concerning acquisitions, interest and income taxes paid for the three-month periods ended March 31, 2019 and 2018.



(In millions)	2019			2018
Assets acquired, excluding cash	$	180		$	35
Liabilities assumed	(5		)	(4		)
Contingent/deferred purchase consideration	(35		)	(7		)
Net cash outflow for current year acquisitions	$	140		$	24



(In millions)	2019		2018
Interest paid	$	98	$	80
Income taxes paid, net of refunds	$	131	$	128

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Other Comprehensive Income (Loss) (Tables)

3 Months Ended

Mar. 31, 2019

Equity [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss)



(In millions)	Unrealized Investment Gains (Losses)		Pension/Post-Retirement Plans Gains (Losses)			Foreign Currency Translation Gains (Losses)			Total Gains (Losses)
Balance as of December 31, 2018	$	—	$	(2,953	)	$	(1,694	)	$	(4,647	)
Other comprehensive (loss) income before reclassifications	—		(59		)	94			35
Amounts reclassified from accumulated other comprehensive income	—		22			—			22
Net current period other comprehensive (loss) income	—		(37		)	94			57
Balance as of March 31, 2019	$	—	$	(2,990	)	$	(1,600	)	$	(4,590	)



(In millions)	Unrealized Investment Gains (Losses)			Pension/Post-Retirement Plans Gains (Losses)			Foreign Currency Translation Gains (Losses)			Total Gains (Losses)
Balance as of December 31, 2017	$	14		$	(2,892	)	$	(1,165	)	$	(4,043	)
Cumulative effect of amended accounting standard	(14		)	—			—			(14		)
Other comprehensive (loss) income before reclassifications	—			(100		)	223			123
Amounts reclassified from accumulated other comprehensive income	—			29			—			29
Net current period other comprehensive (loss) income	—			(71		)	223			152
Balance as of March 31, 2018	$	—		$	(2,963	)	$	(942	)	$	(3,905	)

Schedule of Components of Comprehensive Income (Loss)

The components of other comprehensive income (loss) for the three-month period ended March 31, 2019 and 2018 are as follows:



Three Months Ended March 31,	2019									2018
(In millions)	Pre-Tax			Tax (Credit)			Net of Tax			Pre-Tax			Tax (Credit)			Net of Tax
Foreign currency translation adjustments	$	96		$	2		$	94		$	228		$	5		$	223
Pension/post-retirement plans:
Amortization of (gains) losses included in net periodic pension cost:
Prior service credits (a)	(1		)	—			(1		)	(1		)	—			(1		)
Net actuarial losses (a)	26			6			20			37			7			30
Effect of settlement (a)	4			1			3			—			—			—
Subtotal	29			7			22			36			7			29
Foreign currency translation adjustments	(72		)	(13		)	(59		)	(120		)	(20		)	(100		)
Pension/post-retirement plans (loss) gains	(43		)	(6		)	(37		)	(84		)	(13		)	(71		)
Other comprehensive income (loss)	$	53		$	(4	)	$	57		$	144		$	(8	)	$	152
(a) Components of net periodic pension cost are included in other net benefit credits in the consolidated statements of income. Tax on prior service costs and net actuarial losses is included in income tax expense.

XML 51 R33.htm IDEA: XBRL DOCUMENT

Acquisitions and Dispositions (Tables)

3 Months Ended

Mar. 31, 2019

Business Combinations [Abstract]

Schedule For Allocation of Acquisition Costs

The following table presents the preliminary allocation of the acquisition cost to the assets acquired and liabilities assumed during 2019 based on their fair values:



For the Three Months Ended March 31, 2019
(In millions)
Cash	$	142
Estimated fair value of deferred/contingent consideration	35
Total consideration	$	177
Allocation of purchase price:
Cash and cash equivalents	$	2
Accounts receivable, net	5
Property, plant, and equipment	1
Other intangible assets	71
Goodwill	97
Other assets	6
Total assets acquired	182
Current liabilities	5
Other liabilities	—
Total liabilities assumed	5
Net assets acquired	$	177

Schedule of Acquired Finite-Lived Intangible Assets by Major Class

The following chart provides information about other intangible assets acquired during 2019:

Pro-Forma Information

The unaudited pro-forma financial data is presented for illustrative purposes only and is not necessarily indicative of the operating results that would have been achieved if such acquisitions had occurred on the dates indicated, nor is it necessarily indicative of future consolidated results.



	Three Months Ended March 31,
(In millions, except per share figures)	2019		2018
Revenue	$	4,080	$	4,098
Net income attributable to the Company	$	717	$	694
Basic net income per share attributable to the Company	$	1.42	$	1.37
Diluted net income per share attributable to the Company	$	1.40	$	1.35

XML 52 R34.htm IDEA: XBRL DOCUMENT

Goodwill and Other Intangibles (Tables)

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Changes in the Carrying Amount of Goodwill

Changes in the carrying amount of goodwill are as follows:



March 31,
(In millions)	2019		2018
Balance as of January 1,	$	9,599	$	9,089
Goodwill acquired	97		15
Other adjustments^(a)	43		90
Balance at March 31,	$	9,739	$	9,194

^(a) Primarily reflects the impact of foreign exchange.

Amortized Intangible Assets

The gross cost and accumulated amortization at March 31, 2019 and December 31, 2018 are as follows:



	March 31, 2019						December 31, 2018
(In millions)	Gross Cost		Accumulated Amortization		Net Carrying Amount		Gross Cost		Accumulated Amortization		Net Carrying Amount
Client Relationships	$	2,046	$	685	$	1,361	$	1,970	$	639	$	1,331
Other ^(a)	267		164		103		259		153		106
Amortized intangibles	$	2,313	$	849	$	1,464	$	2,229	$	792	$	1,437

^(a) Primarily non-compete agreements, trade names and developed technology.

Estimated Future Aggregate Amortization Expense

The estimated future aggregate amortization expense is as follows:



For the Years Ending December 31,
(In millions)	Estimated Expense
2019 (excludes amortization through March 31, 2019)	$	151
2020	187
2021	174
2022	159
2023	156
Subsequent years	637
	$	1,464

XML 53 R35.htm IDEA: XBRL DOCUMENT

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following fair value hierarchy table presents information about the Company’s assets and liabilities measured at fair value on a recurring basis as of March 31, 2019 and December 31, 2018.



	Identical Assets (Level 1)				Observable Inputs (Level 2)				Unobservable Inputs (Level 3)				Total
(In millions)	03/31/19		12/31/18		03/31/19		12/31/18		03/31/19		12/31/18		03/31/19		12/31/18
Assets:
Financial instruments owned:
Exchange traded equity securities^(a)	$	21	$	133	$	—	$	—	$	—	$	—	$	21	$	133
Mutual funds^(a)	145		151		—		—		—		—		145		151
Money market funds^(b)	67		118		—		—		—		—		67		118
Other equity investment^(a)	—		—		8		8		—		—		8		8
Total assets measured at fair value	$	233	$	402	$	8	$	8	$	—	$	—	$	241	$	410
Fiduciary Assets:
U.S. Treasury Bills	$	—	$	20	$	—	$	—	$	—	$	—	$	—	$	20
Money market funds	60		80		—		—		—		—		60		80
Total fiduciary assets measured at fair value	$	60	$	100	$	—	$	—	$	—	$	—	$	60	$	100
Liabilities:
Contingent purchase consideration liability^(c)	$	—	$	—	$	—	$	—	$	171	$	183	$	171	$	183
Acquisition related derivative contracts	—		—		—		116		283		325		283		441
Total liabilities measured at fair value	$	—	$	—	$	—	$	116	$	454	$	508	$	454	$	624

^(a)Included in other assets in the consolidated balance sheets.

^(b) Included in cash and cash equivalents in the consolidated balance sheets.

^(c) Included in accounts payable and accrued liabilities and other liabilities in the consolidated balance sheets.

Changes in Fair Value of Level 3 Liabilities Representing Acquisition Related Contingent Consideration

The table below sets forth a summary of the changes in fair value of the Company’s Level 3 liabilities for the three month periods ended March 31, 2019 and 2018:



	Three Months Ended March 31,
(In millions)	2019			2018
Balance at beginning of period,	$	508		$	189
Additions	11			6
Payments	(35		)	(40		)
Revaluation Impact	11			5
Change in fair value of the FX contract	(42		)	—
Other ^(a)	1			1
Balance at March 31,	$	454		$	161

^(a)Primarily reflects the impact of foreign exchange.

XML 54 R36.htm IDEA: XBRL DOCUMENT

Leases (Tables)

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Lease Cost and Additional Information

The following chart provides additional information about the Company’s property leases:



For the Three Months Ended March 31,
(In millions)	2019
Lease Cost:
Operating lease cost	$	82
Short-term lease cost	1
Variable lease cost	37
Sublease income	(4		)
Net lease cost	$	116
Other information:
Operating cash outflows from operating leases	$	87
Right of use assets obtained in exchange for new operating lease liabilities	—
Weighted-average remaining lease term – real estate	7.7 years
Weighted-average discount rate – real estate leases	3.12		%

Future Minimum Lease Payments for Operating Leases

Future minimum lease payments for the Company’s operating leases as of March 31, 2019 are as follows:



Payment Dates	Real Estate Leases
Remainder of 2019	$	262
2020	328
2021	276
2022	257
2023	220
2024	183
Subsequent years	610
Total future lease payments	2,136
Less: Imputed interest	(255		)
Total	$	1,881
Current lease liabilities	$	291
Long-term lease liabilities	1,590
Total lease liabilities	$	1,881

Note: Table excludes obligations for leases with original terms of 12 months or less which have not been recognized as a right to use asset or liability in the consolidated balance sheets.

Aggregate Fixed Future Minimum Commitments

At December 31, 2018, the aggregate future minimum rental commitments under all non-cancelable operating lease agreements are as follows:



For the Year Ended December 31,	Gross Rental Commitments		Rentals from Subleases		Net Rental Commitments
(In millions of dollars)	Gross Rental Commitments		Rentals from Subleases		Net Rental Commitments
2019	$	361	$	32	$	329
2020	$	340	$	31	$	309
2021	$	277	$	12	$	265
2022	$	252	$	10	$	242
2023	$	214	$	9	$	205
Subsequent years	$	753	$	32	$	721

XML 55 R37.htm IDEA: XBRL DOCUMENT

Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2019

Defined Benefit Plan [Abstract]

Schedule of Net Benefit Costs

The components of the net periodic benefit cost for defined benefit and other post-retirement plans are as follows:



Combined U.S. and significant non-U.S. plans	Pension Benefits						Post-retirement Benefits
For the Three Months Ended March 31,	Pension Benefits						Post-retirement Benefits
(In millions)	2019			2018			2019			2018
Service cost	$	8		$	10		$	—		$	—
Interest cost	119			118			1			1
Expected return on plan assets	(213		)	(221		)	—			—
Amortization of prior service (credit) cost	—			—			(1		)	(1		)
Recognized actuarial loss	26			37			—			—
Net periodic benefit (credit) cost	$	(60	)	$	(56	)	$	—		$	—
Settlement loss	4			—			—			—
Total (credit) cost	$	(56	)	$	(56	)	$	—		$	—



Amounts Recorded in the Consolidated Statement of Income
Combined U.S. and significant non-U.S. plans	Pension Benefits						Post-retirement Benefits
For the Three Months Ended March 31,	Pension Benefits						Post-retirement Benefits
(In millions)	2019			2018			2019		2018
Compensation and benefits expense (Operating income)	$	8		$	10		$	—	$	—
Other net benefit (credits) cost	(64		)	(66		)	—		—
Total (credit) cost	$	(56	)	$	(56	)	$	—	$	—



U.S. Plans only	Pension Benefits						Post-retirement Benefits
For the Three Months Ended March 31,	Pension Benefits						Post-retirement Benefits
(In millions)	2019			2018			2019		2018
Interest cost	60			59			—		—
Expected return on plan assets	(86		)	(89		)	—		—
Recognized actuarial loss	11			13			—		—
Net periodic benefit (credit) cost	$	(15	)	$	(17	)	$	—	$	—



Significant non-U.S. plans only	Pension Benefits						Post-retirement Benefits
For the Three Months Ended March 31,	Pension Benefits						Post-retirement Benefits
(In millions)	2019			2018			2019			2018
Service cost	$	8		$	10		$	—		$	—
Interest cost	59			59			1			1
Expected return on plan assets	(127		)	(132		)	—			—
Amortization of prior service credit	—			—			(1		)	(1		)
Recognized actuarial loss	15			24			—			—
Net periodic benefit (credit) cost	$	(45	)	$	(39	)	$	—		$	—
Settlement loss	4			—			—			—
Total (credit) cost	$	(41	)	$	(39	)	$	—		$	—

Schedule of Assumptions Used

The weighted average actuarial assumptions utilized to calculate the net periodic benefit costs for the U.S. and significant non-U.S. defined benefit plans are as follows:



Combined U.S. and significant non-U.S. plans	Pension Benefits				Post-retirement Benefits
Combined U.S. and significant non-U.S. plans	Pension Benefits				Post-retirement Benefits
March 31,	2019		2018		2019		2018
Weighted average assumptions:
Expected return on plan assets	5.74	%	5.83	%	—		—
Discount Rate	3.48	%	3.07	%	3.65	%	3.21	%
Rate of compensation increase	1.74	%	1.73	%	—		—

XML 56 R38.htm IDEA: XBRL DOCUMENT

Debt (Tables)

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Schedule of Outstanding Debt

The Company’s outstanding debt is as follows:



(In millions)	March 31, 2019		December 31, 2018
Short-term:
Commercial paper	$	748	$	—
Current portion of long-term debt	814		314
	1,562		314
Long-term:
Senior notes – 2.35% due 2019	300		300
Senior notes – 2.35% due 2020	499		499
Senior notes – 3.50% due 2020	697		—
Senior notes – 4.80% due 2021	499		499
Senior notes - Floating rate due 2021	298		—
Senior notes – 2.75% due 2022	498		497
Senior notes – 3.30% due 2023	348		348
Senior notes – 4.05% due 2023	249		249
Senior notes – 3.50% due 2024	597		597
Senior notes – 3.875% due 2024	992		—
Senior notes – 3.50% due 2025	497		496
Senior notes – 1.349% due 2026	623		—
Senior notes – 3.75% due 2026	597		596
Senior notes – 4.375% due 2029	1,499		—
Senior notes – 1.979% due 2030	622		—
Senior notes – 5.875% due 2033	298		297
Senior notes – 4.75% due 2039	494		—
Senior notes – 4.35% due 2047	492		492
Senior notes – 4.20% due 2048	592		592
Senior notes – 4.90% due 2049	1,236		—
Mortgage – 5.70% due 2035	355		358
Other	4		4
	12,286		5,824
Less current portion	814		314
	$	11,472	$	5,510

Estimated Fair Value Of Significant Financial Instruments



	March 31, 2019				December 31, 2018
(In millions)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Short-term debt	$	1,562	$	1,561	$	314	$	313
Long-term debt	$	11,472	$	11,943	$	5,510	$	5,437

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

XML 57 R39.htm IDEA: XBRL DOCUMENT

Restructuring Costs (Tables)

3 Months Ended

Mar. 31, 2019

Restructuring and Related Activities [Abstract]

Restructuring Activities

Details of the restructuring activity from January 1, 2018 through March 31, 2019, which includes liabilities from actions prior to 2019, are as follows:



(In millions)	Liability at 1/1/18		Amounts Accrued		Cash Paid			Other			Liability at 12/31/18		Amounts Accrued		Cash Paid			Other		Liability at 3/31/19
Severance	$	15	$	137	$	(77	)	$	(2	)	$	73	$	37	$	(37	)	$	—	$	73
Future rent under non-cancelable leases and other costs	50		24		(37		)	2			39		1		(4		)	2		38
Total	$	65	$	161	$	(114	)	$	—		$	112	$	38	$	(41	)	$	2	$	111

XML 58 R40.htm IDEA: XBRL DOCUMENT

Segment Information (Tables)

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Selected Information And Details For MMC's Operating Segments

Selected information about the Company’s operating segments for the three-month periods ended March 31, 2019 and 2018 are as follows:



	Three Months Ended March 31,
(In millions)	Revenue				Operating Income (Loss)
2019–
Risk and Insurance Services	$	2,423		^(a)	$	733
Consulting	1,673			^(b)	279
Total Operating Segments	4,096				1,012
Corporate/Eliminations	(25		)		(74		)
Total Consolidated	$	4,071			$	938
2018–
Risk and Insurance Services	$	2,344		^(a)	$	716
Consulting	1,668			^(b)	247
Total Operating Segments	4,012				963
Corporate/Eliminations	(12		)		(55		)
Total Consolidated	$	4,000			$	908

Details of Operating Segment Revenue

Details of operating segment revenue for the three-month periods ended March 31, 2019 and 2018 are as follows:



	Three Months Ended March 31,
(In millions)	2019			2018
Risk and Insurance Services
Marsh	$	1,753		$	1,703
Guy Carpenter	670			641
Total Risk and Insurance Services	2,423			2,344
Consulting
Mercer	1,155			1,171
Oliver Wyman Group	518			497
Total Consulting	1,673			1,668
Total Operating Segments	4,096			4,012
Corporate/Eliminations	(25		)	(12		)
Total	$	4,071		$	4,000

XML 59 R41.htm IDEA: XBRL DOCUMENT

Nature of Operations (Details)	3 Months Ended
Nature of Operations (Details)	Mar. 31, 2019 segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of business segments	2

XML 60 R42.htm IDEA: XBRL DOCUMENT

Principles of Consolidation And Other Matters (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019	Dec. 31, 2018
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Operating funds related to regulatory requirements or as collateral under captive insurance arrangements	$ 196,000,000
Equity method investments lag period	3 months
Gain (loss) on investment income, net	$ 5,000,000	$ (1,000,000)
Gains on equity investments	3,000,000
Equity method income	2,000,000	$ 7,000,000
Operating lease, liability	1,881,000,000
Operating lease, right-of-use asset	$ 1,625,000,000			$ 0
Effective tax rate (as a percent)	23.00%	23.90%
Excess tax benefit related to share-based payments (percent)	3.20%	2.40%
Unrecognized tax benefits	$ 74,000,000			$ 78,000,000
Minimum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Reasonably possible decrease in unrecognized tax benefits	0
Maximum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Reasonably possible decrease in unrecognized tax benefits	$ 10,000,000
Accounting Standards Update 2016-02
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Operating lease, liability			$ 1,900,000,000
Operating lease, right-of-use asset			1,700,000,000
Restatement Adjustment \| Accounting Standards Update 2016-02
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Other liabilities			$ 200,000,000

XML 61 R43.htm IDEA: XBRL DOCUMENT

Revenue - Narrative (Details) $ in Millions	3 Months Ended
Revenue - Narrative (Details) $ in Millions	Mar. 31, 2019 USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Percentage of total revenue	1.00%
Contract with customer, asset, additions	$ 128
Contract with customer, asset, reclassified to receivable	42
Contract with customer, liability, revenue recognized	169
Performance obligation satisfied in previous period	17
Marsh Insurance Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, remaining performance obligation	$ 30
Mercer Consulting Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Consulting revenue, payment terms (in days)	30 days
Revenue, remaining performance obligation	$ 429
Oliver Wyman Group Consulting Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, remaining performance obligation	$ 3
Risk and Insurance Services Segment
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Insurance brokerage commissions, payment terms (in days)	30 days
Health Brokerage and Consulting
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer, percent	65.00%
Minimum \| Oliver Wyman Group Consulting Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Consulting revenue, payment terms (in days)	30 days
Minimum \| Risk and Insurance Services Segment
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Estimated brokerage revenue, payment terms (in months)	12 months
Reinsurance brokerage revenue, payment terms (in months)	12 months
Maximum \| Oliver Wyman Group Consulting Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Consulting revenue, payment terms (in days)	60 days
Maximum \| Risk and Insurance Services Segment
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Estimated brokerage revenue, payment terms (in months)	18 months
Reinsurance brokerage revenue, payment terms (in months)	18 months

XML 62 R44.htm IDEA: XBRL DOCUMENT

Revenue - Disaggregation of Revenue (Details) $ in Millions	3 Months Ended
Revenue - Disaggregation of Revenue (Details) $ in Millions	Mar. 31, 2019 USD ($)
Risk and Insurance Services Segment
Disaggregation of Revenue [Line Items]
Revenue	$ 2,423
Fiduciary interest income	23
Risk and Insurance Services Segment \| EMEA
Disaggregation of Revenue [Line Items]
Revenue	633
Risk and Insurance Services Segment \| Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue	165
Risk and Insurance Services Segment \| Latin America
Disaggregation of Revenue [Line Items]
Revenue	78
Risk and Insurance Services Segment \| Total International
Disaggregation of Revenue [Line Items]
Revenue	876
Risk and Insurance Services Segment \| U.S./Canada
Disaggregation of Revenue [Line Items]
Revenue	861
Consulting Segment
Disaggregation of Revenue [Line Items]
Revenue	1,673
Total Wealth \| Consulting Segment
Disaggregation of Revenue [Line Items]
Revenue	543
Health \| Consulting Segment
Disaggregation of Revenue [Line Items]
Revenue	442
Career \| Consulting Segment
Disaggregation of Revenue [Line Items]
Revenue	170
Marsh Insurance Group \| Risk and Insurance Services Segment
Disaggregation of Revenue [Line Items]
Revenue	1,737
Guy Carpenter Reinsurance Group \| Risk and Insurance Services Segment
Disaggregation of Revenue [Line Items]
Revenue	663
Marsh & Guy Carpenter \| Risk and Insurance Services Segment
Disaggregation of Revenue [Line Items]
Revenue	2,400
Mercer Consulting Group \| Consulting Segment
Disaggregation of Revenue [Line Items]
Revenue	1,155
Oliver Wyman Group Consulting Group \| Consulting Segment
Disaggregation of Revenue [Line Items]
Revenue	$ 518

XML 63 R45.htm IDEA: XBRL DOCUMENT

Revenue - Contract Assets and Contract Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract Assets	$ 198	$ 112
Contract Liabilities	$ 611	$ 545

XML 64 R46.htm IDEA: XBRL DOCUMENT

Revenue - Estimated Revenue Expected to Be Recognized Related to Performance Obligations (Details) $ in Millions	Mar. 31, 2019 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 190
Revenue, remaining performance obligation, expected timing of satisfaction, period (in years)	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 130
Revenue, remaining performance obligation, expected timing of satisfaction, period (in years)	2 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 81
Revenue, remaining performance obligation, expected timing of satisfaction, period (in years)	3 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 44
Revenue, remaining performance obligation, expected timing of satisfaction, period (in years)	4 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 17
Revenue, remaining performance obligation, expected timing of satisfaction, period (in years)

XML 65 R47.htm IDEA: XBRL DOCUMENT

Fiduciary Assets and Liabilities (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Fiduciary Assets and Liabilities [Line Items]
Net uncollected premiums and claims receivable and payable	$ 9,200		$ 7,300
Risk and Insurance Services Segment
Fiduciary Assets and Liabilities [Line Items]
Interest on fiduciary funds	23
Operating Segments \| Risk and Insurance Services Segment
Fiduciary Assets and Liabilities [Line Items]
Interest on fiduciary funds	23	$ 13
Operating Segments \| Consulting Segment
Fiduciary Assets and Liabilities [Line Items]
Interest on fiduciary funds	$ 1	$ 1

XML 66 R48.htm IDEA: XBRL DOCUMENT

Per Share Data (Basic and Diluted EPS Calculation Continuing Operations) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net income before non-controlling interests	$ 727	$ 696
Less: Net income attributable to non-controlling interests	11	6
Net income attributable to the Company	$ 716	$ 690
Basic weighted average common shares outstanding (in shares)	505	508
Dilutive effect of potentially issuable common shares (in shares)	6	6
Diluted weighted average common shares outstanding (in shares)	511	514
Average stock price used to calculate common stock equivalents (in dollars per share)	$ 88.54	$ 82.83

XML 67 R49.htm IDEA: XBRL DOCUMENT

Supplemental Disclosures to the Consolidated Statements of Cash Flows (Additional Information Concerning Acquisitions, Interest And Income Taxes Paid) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Supplemental Cash Flow Information [Abstract]
Assets acquired, excluding cash	$ 180	$ 35
Liabilities assumed	(5)	(4)
Contingent/deferred purchase consideration	(35)	(7)
Net cash outflow for current year acquisitions	140	24
Interest paid	98	80
Income taxes paid, net of refunds	$ 131	$ 128

XML 68 R50.htm IDEA: XBRL DOCUMENT

Supplemental Disclosures to the Consolidated Statements of Cash Flows (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Supplemental Cash Flow Information [Abstract]
Deferred and contingent consideration from prior years acquisition	$ 29	$ 70
Deferred purchase consideration from prior years' acquisitions	23	40
Contingent consideration from prior year's acquisitions	6	30
Net charge for adjustments related to acquisition related accounts	11	5
Payment of contingent consideration	29	10
Non-cash issuance of common stock	158	125
Stock-based compensation expense, equity awards	57	50
Proceeds from issuance of debt	6,462	$ 592
Interest income	25
Acquisition-related hedging payments	129
Right-of-use asset, noncash	1,700
Right-to-use liability, noncash	$ 1,900

XML 69 R51.htm IDEA: XBRL DOCUMENT

Other Comprehensive Income (Loss) (Schedule of Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of amended accounting standard			$ (14)
Other comprehensive (loss) income before reclassifications	$ 35	$ 123
Amounts reclassified from accumulated other comprehensive income	22	29
Other comprehensive income, net of tax	57	152
Unrealized Investment Gains (Losses)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	0	14
Cumulative effect of amended accounting standard			(14)
Other comprehensive (loss) income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income, net of tax	0	0
Balance, ending of period	0	0
Pension/Post-Retirement Plans Gains (Losses)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(2,953)	(2,892)
Cumulative effect of amended accounting standard			0
Other comprehensive (loss) income before reclassifications	(59)	(100)
Amounts reclassified from accumulated other comprehensive income	22	29
Other comprehensive income, net of tax	(37)	(71)
Balance, ending of period	(2,990)	(2,963)
Foreign Currency Translation Gains (Losses)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(1,694)	(1,165)
Cumulative effect of amended accounting standard			$ 0
Other comprehensive (loss) income before reclassifications	94	223
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income, net of tax	94	223
Balance, ending of period	(1,600)	(942)
AOCI Attributable to Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(4,647)	(4,043)
Other comprehensive income, net of tax	57	152
Balance, ending of period	$ (4,590)	$ (3,905)

XML 70 R52.htm IDEA: XBRL DOCUMENT

Other Comprehensive Income (Loss) (Schedule Of Components Of Comprehensive Income (Loss)) (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2019

Mar. 31, 2018

Equity [Abstract]

Foreign currency translation adjustments, Pre-Tax

$ 96

$ 228

Foreign currency translation adjustments, Tax

Foreign currency translation adjustments, Net of Tax

223

Pension/post-retirement plans:

Prior services credits, Pre-Tax

^[1]

(1)

Prior service credits, Tax

^[1]

Prior service credits, Net of Tax

^[1]

(1)

Net actuarial loss, Pre-Tax

^[1]

Net actuarial loss, Tax

^[1]

Net actuarial loss, Net of Tax

^[1]

Effect of settlement, Pre-tax

^[1]

Effect of settlement, Tax

^[1]

Effect of settlement, Net of Tax

^[1]

Subtotal, Pre-Tax

Subtotal, Tax

Subtotal, Net of Tax

Foreign currency translation adjustment, Pre-Tax

(72)

(120)

Foreign currency translation adjustment, Tax

(13)

(20)

Foreign currency translation adjustment, Net of Tax

(59)

(100)

Pension/post-retirement plans (losses) gains, Pre-Tax

(43)

(84)

Pension/post-retirement plans (losses) gains, Tax

(6)

(13)

Pension/post-retirement plans (losses) gains, Net of Tax

(37)

(71)

Other comprehensive income, before tax

144

Other comprehensive (loss) income, Tax

(4)

(8)

Other comprehensive income, net of tax

$ 57

$ 152

[1]	Components of net periodic pension cost are included in compensation and benefits in the Consolidated Statements of Income. Tax on prior service gains and net actuarial losses is included in income tax expense.

XML 71 R53.htm IDEA: XBRL DOCUMENT

Acquisitions and Dispositions (Narrative) (Details) £ / shares in Units, $ in Millions, £ in Billions				3 Months Ended		12 Months Ended
	Apr. 01, 2019 USD ($)	Apr. 01, 2019 GBP (£) £ / shares	Sep. 20, 2018 GBP (£)	Mar. 31, 2019 USD ($) acquisition	Mar. 31, 2018 USD ($)	Dec. 31, 2018 acquisition	Jan. 01, 2019
Business Acquisition [Line Items]
Total consideration				$ 177	$ 36
Cash				142	29
Estimated fair value of deferred/contingent consideration				35	7
Deferred purchase consideration from prior years' acquisitions				23	40
Contingent consideration from prior year's acquisitions				6	30
Assumption of debt				5	4
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Total consideration				177
Cash				142
Estimated fair value of deferred/contingent consideration				35
Revenue related to acquisitions				4	3
Operating (loss) income related to acquisitions				1	(1)
Prior Fiscal Periods Acquisitions
Business Acquisition [Line Items]
Deferred purchase consideration from prior years' acquisitions					40
Contingent consideration from prior year's acquisitions				$ 35	$ 40
Jardine Lloyd Thompson Group plc
Business Acquisition [Line Items]
Total consideration \| £			£ 5.2
Risk and Insurance Services Segment
Business Acquisition [Line Items]
Number of acquisitions made (in acquisitions) \| acquisition				2		12
Consulting Segment
Business Acquisition [Line Items]
Number of acquisitions made (in acquisitions) \| acquisition						8
Minimum
Business Acquisition [Line Items]
Revenue target period (in years)				2 years
Minimum \| Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Revenue target period (in years)				2 years
Maximum
Business Acquisition [Line Items]
Revenue target period (in years)				4 years
Maximum \| Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Revenue target period (in years)				4 years
Subsequent Event \| Jardine Lloyd Thompson Group plc
Business Acquisition [Line Items]
Total consideration \| £		£ 5.2
Business acquisition, share price (in usd per share) \| £ / shares		£ 19.15
Equity interests issued and issuable	$ 5,600	£ 4.3
Assumption of debt	$ 1,000
Marsh India
Business Acquisition [Line Items]
Percentage of ownership in equity investment						26.00%	49.00%

XML 72 R54.htm IDEA: XBRL DOCUMENT

Acquisitions and Dispositions (Allocation Of Acquisition Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Cash	$ 142	$ 29
Estimated fair value of deferred/contingent consideration	35	7
Total consideration	177	36
Allocation of purchase price:
Goodwill	9,739	$ 9,194	$ 9,599	$ 9,089
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Cash	142
Estimated fair value of deferred/contingent consideration	35
Total consideration	177
Allocation of purchase price:
Cash and cash equivalents	2
Accounts receivable, net	5
Property, plant, and equipment	1
Other intangible assets	71
Goodwill	97
Other assets	6
Total assets acquired	182
Current liabilities	5
Other liabilities	0
Total liabilities assumed	5
Net assets acquired	$ 177

XML 73 R55.htm IDEA: XBRL DOCUMENT

Acquisitions and Dispositions (Acquired Finite-Lived Intangible Assets) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 71
Client relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 67
Finite-lived intangible assets, remaining amortization period	11 years
Other
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 4
Finite-lived intangible assets, remaining amortization period	5 years

XML 74 R56.htm IDEA: XBRL DOCUMENT

Acquisitions and Dispositions (Pro-Forma Information) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Business Combinations [Abstract]
Revenue	$ 4,080	$ 4,098
Net income attributable to the Company	$ 717	$ 694
Basic net income per share:
Basic net income per share attributable to the Company (in dollars per share)	$ 1.42	$ 1.37
Diluted net income per share:
Diluted net income per share attributable to the Company (in dollars per share)	$ 1.40	$ 1.35

XML 75 R57.htm IDEA: XBRL DOCUMENT

Goodwill and Other Intangibles (Changes in the Carrying Amount of Goodwill) (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2019

Mar. 31, 2018

Goodwill [Roll Forward]

Balance as of January 1,

$ 9,599

$ 9,089

Goodwill acquired

Other adjustments

^[1]

Balance at March 31,

$ 9,739

$ 9,194

[1]	Primarily reflects the impact of foreign exchange.

XML 76 R58.htm IDEA: XBRL DOCUMENT

Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Goodwill acquired	$ 97	$ 15
Goodwill	9,739	9,194	$ 9,599	$ 9,089
Aggregate amortization expense	51	$ 45
Risk and Insurance Services Segment
Segment Reporting Information [Line Items]
Goodwill	6,900
Consulting Segment
Segment Reporting Information [Line Items]
Goodwill	$ 2,800

XML 77 R59.htm IDEA: XBRL DOCUMENT

Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($)
$ in Millions

Mar. 31, 2019

Dec. 31, 2018

Finite-Lived Intangible Assets [Line Items]

Gross Cost

$ 2,313

$ 2,229

Accumulated Amortization

849

792

Net Carrying Amount

1,464

1,437

Client relationships

Finite-Lived Intangible Assets [Line Items]

Gross Cost

2,046

1,970

Accumulated Amortization

685

639

Net Carrying Amount

1,361

1,331

Other

Finite-Lived Intangible Assets [Line Items]

Gross Cost

^[1]

267

259

Accumulated Amortization

^[1]

164

153

Net Carrying Amount

^[1]

$ 103

$ 106

[1]	Primarily non-compete agreements, trade names and developed technology.

XML 78 R60.htm IDEA: XBRL DOCUMENT

Goodwill And Other Intangibles (Estimated Future Aggregate Amortization Expense) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
2019 (excludes amortization through March 31, 2019)	$ 151
2020	187
2021	174
2022	159
2023	156
Subsequent years	637
Net Carrying Amount	$ 1,464	$ 1,437

XML 79 R61.htm IDEA: XBRL DOCUMENT

Fair Value Measurements (Narrative) (Details) $ / shares in Units, shares in Millions, $ in Millions, £ in Billions			1 Months Ended		3 Months Ended
	Apr. 01, 2019 GBP (£)	Sep. 20, 2018 GBP (£)	Apr. 26, 2019 USD ($)	Mar. 31, 2019 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2019 R / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2014 R / shares
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total consideration					$ 177		$ 36
Net charge for adjustments related to acquisition related accounts					11		5
Increase in fair value of contingent consideration due to 5% increase in projections					44
Decrease in fair value of contingent consideration due to 5% decrease in projections					36
Carrying value of investment				$ 388	388				$ 287
Equity method income					2		7
Other investments				74	$ 74				75
Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revenue target period (in years)					2 years
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revenue target period (in years)					4 years
Private Insurance and Consulting
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of investment				155	$ 155				61
Private Equity Funds, Non-US
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of investment				84	84				82
Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value				$ 35	$ 35				146
Alexander Forbes Group Holdings Limited
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Share price (per share amount) \| R / shares								R 5.03		R 7.50
Percentage of ownership in equity investment				33.00%	33.00%
Carrying value of investment				$ 149	$ 149
Other than temporary impairment						$ 83
Shares owned in investment (in shares) \| shares				443	443
Equity method investment, quoted market value				$ 157	$ 157
Benefitfocus
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unrealized investment (losses) gains					3		$ (8)
Proceeds from sale of other investments				$ 132	$ 115
Jardine Lloyd Thompson Group plc
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total consideration \| £		£ 5.2
Treasury Lock \| Jardine Lloyd Thompson Group plc
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative hedges, assets									$ 2,000
Money Market Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Share price (per share amount) \| $ / shares				$ 1.00	$ 1.00
Subsequent Event \| Benefitfocus
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Proceeds from sale of other investments			$ 17
Subsequent Event \| Jardine Lloyd Thompson Group plc
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total consideration \| £	£ 5.2

XML 80 R62.htm IDEA: XBRL DOCUMENT

Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - Fair Value, Measurements, Recurring - USD ($)
$ in Millions

Mar. 31, 2019

Dec. 31, 2018

$ 241

$ 410

100

Identical Assets (Level 1)

454

624

233

402

100

Observable Inputs (Level 2)

Unobservable Inputs (Level 3)

116

454

508

US Treasury Bills

US Treasury Bills | Identical Assets (Level 1)

US Treasury Bills | Observable Inputs (Level 2)

US Treasury Bills | Unobservable Inputs (Level 3)

Money Market Funds

Money Market Funds | Identical Assets (Level 1)

Money Market Funds | Observable Inputs (Level 2)

Money Market Funds | Unobservable Inputs (Level 3)

Other Assets

^[1]

133

^[1]

145

151

Other Assets | Identical Assets (Level 1)

^[1]

^[1]

133

^[1]

145

151

Other Assets | Observable Inputs (Level 2)

^[1]

^[1]

^[1]

Other Assets | Unobservable Inputs (Level 3)

^[1]

^[1]

^[1]

Cash and Cash Equivalents

^[1]

Cash and Cash Equivalents | Identical Assets (Level 1)

^[2]

118

Cash and Cash Equivalents | Observable Inputs (Level 2)

^[2]

118

Cash and Cash Equivalents | Unobservable Inputs (Level 3)

^[2]

Accounts Payable and Accrued Liabilities and Other Liabilities

^[2]

Accounts Payable and Accrued Liabilities and Other Liabilities | Identical Assets (Level 1)

^[3]

171

183

Accounts Payable and Accrued Liabilities and Other Liabilities | Observable Inputs (Level 2)

^[3]

Accounts Payable and Accrued Liabilities and Other Liabilities | Unobservable Inputs (Level 3)

^[3]

Accounts Payable and Accrued Liabilities | Forward Contracts

^[3]

171

183

Accounts Payable and Accrued Liabilities | Forward Contracts | Identical Assets (Level 1)

283

441

Accounts Payable and Accrued Liabilities | Forward Contracts | Observable Inputs (Level 2)

Accounts Payable and Accrued Liabilities | Forward Contracts | Unobservable Inputs (Level 3)

116

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]

$ 283

$ 325

[1]	Included in other assets in the consolidated balance sheets.
[2]	Included in cash and cash equivalents in the consolidated balance sheets.
[3]	Included in accounts payable and accrued liabilities and other liabilities in the consolidated balance sheets.

XML 81 R63.htm IDEA: XBRL DOCUMENT

Fair Value Measurements (Changes In Fair Value Of Level 3 Liabilities Representing Acquisition Related Contingent Consideration) (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2019

Mar. 31, 2018

Revaluation Impact

$ 11

$ 5

Contingent Consideration

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]

Balance at beginning of period,

508

189

Additions

Payments

(35)

(40)

Revaluation Impact

Other

^[1]

Balance at March 31,

454

161

Foreign Exchange Forward | Contingent Consideration

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]

Change in fair value of the FX contract

$ (42)

$ 0

[1]	Primarily reflects the impact of foreign exchange.

XML 82 R64.htm IDEA: XBRL DOCUMENT

Derivatives - Narrative (Details) € in Billions, £ in Billions		1 Months Ended		3 Months Ended			12 Months Ended
	Sep. 20, 2018 GBP (£)	Mar. 31, 2019 USD ($)	Jan. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2019 EUR (€)
Derivative [Line Items]
Total consideration					$ 177,000,000	$ 36,000,000
Exchange rate	0.0343
Foreign Exchange Forward
Derivative [Line Items]
Unrealized loss					42,000,000
Treasury Lock
Derivative [Line Items]
Payments for derivative settlement			$ 122,000,000		$ 6,000,000
Jardine Lloyd Thompson Group plc
Derivative [Line Items]
Total consideration \| £	£ 5.2
Jardine Lloyd Thompson Group plc \| Treasury Lock
Derivative [Line Items]
Unrealized loss							$ 116,000,000
Derivative hedges, assets							$ 2,000,000,000
Senior Notes
Derivative [Line Items]
Proceeds from issuance of debt			$ 5,000,000,000
Senior Notes \| Jardine Lloyd Thompson Group plc
Derivative [Line Items]
Proceeds from issuance of debt \| €								€ 1.1
Payments for derivative settlement		$ 7,300,000
Net investment hedge, threshold percentage of the equity balance					80.00%
Scenario, Forecast \| Foreign Exchange Forward
Derivative [Line Items]
Unrealized loss				$ 12,000,000

XML 83 R65.htm IDEA: XBRL DOCUMENT

Leases - Narrative (Details) $ in Millions	3 Months Ended
Leases - Narrative (Details) $ in Millions	Mar. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Percentage of lease obligations used for office space	98.00%
Lessee, operating lease, lease not yet commenced, amount	$ 46
Lessee, operating lease, lease not yet commenced, term (years)	15 months
Minimum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract (years)	10 years
Maximum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract (years)	25 years

XML 84 R66.htm IDEA: XBRL DOCUMENT

Leases - Lease Cost and Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 82
Short-term lease cost	1
Variable lease cost	37
Sublease income	(4)
Net lease cost	116
Operating cash outflows from operating leases	87
Right of use assets obtained in exchange for new operating lease liabilities	$ 0
Real Estate Leases
Lessee, Lease, Description [Line Items]
Weighted-average remaining lease term	7 years 8 months 12 days
Weighted-average discount rate	3.12%

XML 85 R67.htm IDEA: XBRL DOCUMENT

Leases - Future Minimum Payments for Operating Leases (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Remainder of 2019	$ 262
2020	328
2021	276
2022	257
2023	220
2024	183
Subsequent years	610
Total future lease payments	2,136
Less: Imputed interest	(255)
Total	1,881
Current lease liabilities	291	$ 0
Long-term lease liabilities	$ 1,590	$ 0

XML 86 R68.htm IDEA: XBRL DOCUMENT

Leases - Aggregate Fixed Future Minimum Commitments (Details) $ in Millions	Dec. 31, 2018 USD ($)
Gross Rental Commitments
2019, Gross Rental Commitments	$ 361
2020, Gross Rental Commitments	340
2021, Gross Rental Commitments	277
2022, Gross Rental Commitments	252
2023, Gross Rental Commitments	214
Subsequent years, Gross Rental Commitments	753
Rentals from Subleases
2019, Rentals from Subleases	32
2020, Rentals from Subleases	31
2021, Rentals from Subleases	12
2022, Rentals from Subleases	10
2023, Rentals from Subleases	9
Subsequent years, Rentals from Subleases	32
Net Rental Commitments
2019, Net Rental Commitments	329
2020, Net Rental Commitments	309
2021 Net Rental Commitments	265
2022, Net Rental Commitments	242
2023, Net Rental Commitments	205
Subsequent years, Net Rental Commitments	$ 721

XML 87 R69.htm IDEA: XBRL DOCUMENT

Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 21
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in current fiscal year	72
United States
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 35	$ 34
United States \| Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage	64.00%
Actual asset allocation percentage of equity	63.00%
United States \| Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage	36.00%
Actual asset allocation percentage of equity	37.00%
United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 22	$ 22
United Kingdom \| Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage	34.00%
Actual asset allocation percentage of equity	34.00%
United Kingdom \| Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage	66.00%
Actual asset allocation percentage of equity	66.00%
United Kingdom \| Geographic Concentration Risk \| Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Concentration risk percentage	81.00%

XML 88 R70.htm IDEA: XBRL DOCUMENT

Retirement Benefits (Schedule Of Defined Benefit Plan Net Periodic Benefit Cost Combined U.S. and Signficant Non-U.S. Plans) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8	$ 10
Interest cost	119	118
Expected return on plan assets	(213)	(221)
Amortization of prior service (credit) cost	0	0
Recognized actuarial loss	26	37
Net periodic benefit (credit) cost	(60)	(56)
Settlement loss	4	0
Total (credit) cost	(56)	(56)
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	1	1
Expected return on plan assets	0	0
Amortization of prior service (credit) cost	(1)	(1)
Recognized actuarial loss	0	0
Net periodic benefit (credit) cost	0	0
Settlement loss	0	0
Total (credit) cost	0	0
United States \| Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	60	59
Expected return on plan assets	(86)	(89)
Recognized actuarial loss	11	13
Net periodic benefit (credit) cost	(15)	(17)
United States \| Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	0	0
Expected return on plan assets	0	0
Recognized actuarial loss	0	0
Net periodic benefit (credit) cost	0	0
Foreign Plan \| Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	10
Interest cost	59	59
Expected return on plan assets	(127)	(132)
Amortization of prior service (credit) cost	0	0
Recognized actuarial loss	15	24
Net periodic benefit (credit) cost	(45)	(39)
Settlement loss	4	0
Total (credit) cost	(41)	(39)
Foreign Plan \| Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	1	1
Expected return on plan assets	0	0
Amortization of prior service (credit) cost	(1)	(1)
Recognized actuarial loss	0	0
Net periodic benefit (credit) cost	0	0
Settlement loss	0	0
Total (credit) cost	$ 0	$ 0

XML 89 R71.htm IDEA: XBRL DOCUMENT

Retirement Benefits (Schedule Of Defined Benefit Plan Net Periodic Benefit Cost Amounts Recorded in Consolidated Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Compensation and benefits expense (Operating income)	$ (938)	$ (908)
Other net benefit (credits) cost	(64)	(66)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Compensation and benefits expense (Operating income)	8	10
Other net benefit (credits) cost	(64)	(66)
Total (credit) cost	(56)	(56)
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Compensation and benefits expense (Operating income)	0	0
Other net benefit (credits) cost	0	0
Total (credit) cost	$ 0	$ 0

XML 90 R72.htm IDEA: XBRL DOCUMENT

Retirement Benefits (Schedule Of Defined Benefit Plan Weighted Average Assumption Used In Calculating Net Periodic Benefit Cost) (Details)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Benefits
Weighted average assumptions:
Expected return on plan assets	5.74%	5.83%
Discount rate	3.48%	3.07%
Rate of compensation increase	1.74%	1.73%
Postretirement Benefits
Weighted average assumptions:
Expected return on plan assets	0.00%	0.00%
Discount rate	3.65%	3.21%
Rate of compensation increase	0.00%	0.00%

XML 91 R73.htm IDEA: XBRL DOCUMENT

Debt (Schedule Of Outstanding Debt) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Debt Instrument [Line Items]
Commercial paper outstanding	$ 748	$ 0
Current portion of long-term debt	814	314
Short-term debt	1,562	314
Long-term debt, current and noncurrent	12,286	5,824
Long-term debt	11,472	5,510
2.35% Senior Debt Obligations Due 2019
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 300	300
Interest rate	2.35%
2.35% Senior Debt Obligations Due 2020
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 499	499
Interest rate	2.35%
3.50% Senior Debt Obligations Due 2020
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 697	0
Interest rate	3.50%
4.80% Senior Debt Obligations Due 2021
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 499	499
Interest rate	4.80%
Floating Rate Senior Debt Obligations Due 2021
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 298	0
2.75% Senior Debt Obligations Due 2022
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 498	497
Interest rate	2.75%
3.30% Senior Debt Obligations Due 2023
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 348	348
Interest rate	3.30%
4.05% Senior Debt Obligations Due 2023
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 249	249
Interest rate	4.05%
3.50% Senior Debt Obligations Due 2024
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 597	597
Interest rate	3.50%
3.875% Senior Debt Obligations Due 2024
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 992	0
Interest rate	3.875%
3.50% Senior Debt Obligations Due 2025
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 497	496
Interest rate	3.50%
1.349% Senior Debt Obligations Due 2026
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 623	0
Interest rate	1.349%
3.75% Senior Debt Obligations Due 2026
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 597	596
Interest rate	3.75%
4.375% Senior Debt Obligations Due 2029
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 1,499	0
Interest rate	4.375%
1.979% Senior Debt Obligations Due 2030
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 622	0
Interest rate	1.979%
5.875% Senior Debt Obligations Due 2033
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 298	297
Interest rate	5.875%
4.75% Senior Debt Obligations Due 2039
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 494	0
Interest rate	4.75%
4.35% Senior Debt Obligation Due 2047
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 492	492
Interest rate	4.35%
4.20% Senior Debt Obligations Due 2048
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 592	592
Interest rate	4.20%		4.20%
4.90% Senior Debt Obligations Due 2049
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 1,236	0
Interest rate	4.90%
Mortgage Due 2035
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 355	358
Interest rate	5.70%
Other
Debt Instrument [Line Items]
Long-term debt, current and noncurrent	$ 4	$ 4

XML 92 R74.htm IDEA: XBRL DOCUMENT

Debt (Narrative) (Details) £ in Billions	1 Months Ended	3 Months Ended	12 Months Ended
Debt (Narrative) (Details) £ in Billions	Mar. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2019 EUR (€)	Jan. 31, 2019 USD ($)	Oct. 01, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 18, 2018 GBP (£)	Mar. 31, 2018 USD ($)
Debt Instrument [Line Items]
Commercial paper outstanding	$ 748,000,000	$ 748,000,000	$ 0
1.349% Senior Debt Obligations Due 2026
Debt Instrument [Line Items]
Interest rate	1.349%	1.349%		1.349%
1.979% Senior Debt Obligations Due 2030
Debt Instrument [Line Items]
Interest rate	1.979%	1.979%		1.979%
Loan Facility One
Debt Instrument [Line Items]
Debt facilities, maximum borrowing capacity	$ 300,000,000	$ 300,000,000
Loan Facility Two
Debt Instrument [Line Items]
Revolving credit facility, amount outstanding	$ 300,000,000	$ 300,000,000
4.20% Senior Debt Obligations Due 2048
Debt Instrument [Line Items]
Proceeds from issuance of debt									$ 600,000,000
Interest rate	4.20%	4.20%		4.20%					4.20%
Commercial Paper
Debt Instrument [Line Items]
Debt financing program	$ 1,500,000,000	$ 1,500,000,000
Effective interest rate	2.78%	2.78%		2.78%
Jardine Lloyd Thompson Group plc \| Bridge Loan
Debt Instrument [Line Items]
Derivative, notional amount	$ 0	$ 0						£ 5.2
Payments of debt issuance costs			35,000,000
Amortization of debt issuance costs			$ 30,000,000
Interest expense, debt		5,000,000
Senior Notes
Debt Instrument [Line Items]
Proceeds from issuance of debt					$ 5,000,000,000
Senior Notes \| Senior Debt Obligations 3.50% Due 2020
Debt Instrument [Line Items]
Proceeds from issuance of debt					$ 700,000,000
Interest rate					3.50%
Senior Notes \| Senior Debt Obligations 3.875% Due 2024
Debt Instrument [Line Items]
Proceeds from issuance of debt					$ 1,000,000,000
Interest rate					3.875%
Senior Notes \| Senior Debt Obligations 4.375% Due 2029
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 1,500,000,000.0	$ 1,500,000,000.0			$ 1,250,000,000.00
Interest rate					4.375%
Senior Notes \| Senior Debt Obligations 4.75% Due 2039
Debt Instrument [Line Items]
Proceeds from issuance of debt					$ 500,000,000
Interest rate					4.75%
Senior Notes \| Senior Debt Obligations 4.90% Due 2049
Debt Instrument [Line Items]
Proceeds from issuance of debt					$ 1,250,000,000.00
Interest rate					4.90%
Senior Notes \| Floating Rate Senior Notes Due 2021
Debt Instrument [Line Items]
Proceeds from issuance of debt					$ 300,000,000
Senior Notes \| 1.349% Senior Debt Obligations Due 2026
Debt Instrument [Line Items]
Proceeds from issuance of debt \| €				€ 550,000,000
Interest rate	1.349%	1.349%		1.349%
Senior Notes \| 1.979% Senior Debt Obligations Due 2030
Debt Instrument [Line Items]
Proceeds from issuance of debt \| €				€ 550,000,000
Interest rate	1.979%	1.979%		1.979%
Senior Notes \| Senior Debt Obligations 4.375% Due 2019
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 250,000,000	$ 250,000,000
Senior Notes \| Jardine Lloyd Thompson Group plc
Debt Instrument [Line Items]
Proceeds from issuance of debt \| €				€ 1,100,000,000
Term Loan Facility \| Loan Facility One
Debt Instrument [Line Items]
Term of debt	1 year
Term Loan Facility \| Loan Facility Two
Debt Instrument [Line Items]
Term of debt	3 years
Term Loan Facility \| Loan Facilities Closed March 2019
Debt Instrument [Line Items]
Revolving credit facility, amount outstanding	$ 0	0
Revolving Credit Facility \| Amended Revolving Credit Facility March 27, 2014
Debt Instrument [Line Items]
Revolving credit facility, amount outstanding	$ 0	$ 0
Term of debt		5 years
Debt facilities, maximum borrowing capacity						$ 1,800,000,000	$ 1,500,000,000.0

XML 93 R75.htm IDEA: XBRL DOCUMENT

Debt (Estimated Fair Value of Significant Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	$ 1,562	$ 314
Long-term debt	11,472	5,510
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	1,561	313
Long-term debt	$ 11,943	$ 5,437

XML 94 R76.htm IDEA: XBRL DOCUMENT

Restructuring Costs (Restructuring Activities) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Liability at beginning of period	$ 112	$ 65
Amounts Accrued	38	161
Cash Paid	(41)	(114)
Other	2	0
Liability at end of period	111	112
Severance
Restructuring Reserve [Roll Forward]
Liability at beginning of period	73	15
Amounts Accrued	37	137
Cash Paid	(37)	(77)
Other	0	(2)
Liability at end of period	73	73
Future rent under non-cancelable leases and other costs
Restructuring Reserve [Roll Forward]
Liability at beginning of period	39	50
Amounts Accrued	1	24
Cash Paid	(4)	(37)
Other	2	2
Liability at end of period	38	$ 39
Risk and Insurance Services Segment \| Severance and Consulting Costs
Restructuring Reserve [Roll Forward]
Amounts Accrued	5
Mercer Consulting Group \| Severance and Consulting Costs
Restructuring Reserve [Roll Forward]
Amounts Accrued	10
Jardine Lloyd Thompson Group plc \| Acquisition Related
Restructuring Reserve [Roll Forward]
Amounts Accrued	20
Jardine Lloyd Thompson Group plc \| Risk and Insurance Services Segment \| Acquisition Related
Restructuring Reserve [Roll Forward]
Amounts Accrued	19
Corporate, Non-Segment \| Severance and Future Rent Under Non-Cancelable Leases and Other Costs [Member]
Restructuring Reserve [Roll Forward]
Amounts Accrued	3
Corporate, Non-Segment \| Jardine Lloyd Thompson Group plc \| Acquisition Related
Restructuring Reserve [Roll Forward]
Amounts Accrued	$ 1

XML 95 R77.htm IDEA: XBRL DOCUMENT

Common Stock (Details) - USD ($) shares in Millions	3 Months Ended
Common Stock (Details) - USD ($) shares in Millions	Mar. 31, 2019	Mar. 31, 2018	Nov. 30, 2016
Equity, Class of Treasury Stock [Line Items]
Payments for repurchase of common stock	$ 0	$ 250,000,000
Stock-based compensation, shares issued during period	3.2	2.3
Common Stock
Equity, Class of Treasury Stock [Line Items]
Payments for repurchase of common stock	$ 0	$ 250,000,000
Share repurchases program, authorized amount (up to)			$ 2,500,000,000.0
Stock repurchase program, remaining authorized repurchase amount	$ 866,000,000
Common stock repurchased (in shares)		3.0

XML 96 R78.htm IDEA: XBRL DOCUMENT

Claims, Lawsuits And Other Contingencies (Details) £ in Millions	Mar. 31, 2019 GBP (£)
Other Contingencies-Guarantees
Loss Contingencies [Line Items]
Amount reinsured by third party (up to)	£ 40

XML 97 R79.htm IDEA: XBRL DOCUMENT

Segment Information (Selected Information And Details For MMC's Operating Segments) (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2019

Mar. 31, 2018

$ 4,071

$ 4,000

Risk and Insurance Services Segment

938

908

Equity method income

Interest on fiduciary funds

Operating Segments

4,096

4,012

Operating Segments | Risk and Insurance Services Segment

1,012

963

^[1]

2,423

2,344

Interest on fiduciary funds

^[1]

733

716

Equity method income

(1)

Operating Segments | Consulting Segment

^[2]

1,673

1,668

Interest on fiduciary funds

^[2]

279

247

Equity method income

Corporate and Eliminations

(25)

(12)

Intersegment Eliminations | Risk and Insurance Services Segment

(74)

(55)

Intersegment Eliminations | Consulting Segment

$ 24

$ 11

[1]	Includes inter-segment revenue of $1 million in 2019 and 2018, respectively, interest income on fiduciary funds of $23 million and $13 million in 2019 and 2018, respectively, and equity method income (loss) of $2 million and $(1) million in 2019 and 2018, respectively
[2]	Includes inter-segment revenue of $24 million and $11 million in 2019 and 2018, respectively, interest income on fiduciary funds of $1 million in 2019 and 2018, respectively, and equity method income of $5 million and $3 million in 2019 and in 2018, respectively.

XML 98 R80.htm IDEA: XBRL DOCUMENT

Segment Information (Details of Operating Segment Revenue) (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2019

Mar. 31, 2018

$ 4,071

$ 4,000

Operating Segments

Operating Segments | Risk and Insurance Services Segment

4,096

4,012

Operating Segments | Risk and Insurance Services Segment | Marsh Insurance Group

^[1]

2,423

2,344

Operating Segments | Risk and Insurance Services Segment | Guy Carpenter Reinsurance Group

1,753

1,703

Operating Segments | Consulting Segment

670

641

Operating Segments | Consulting Segment | Mercer Consulting Group

^[2]

1,673

1,668

Operating Segments | Consulting Segment | Oliver Wyman Group Consulting Group

1,155

1,171

Corporate and Eliminations

518

497