Revenue, Percent

No definition available.

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- Definition

Revenue from Contract with Customer, Percent

+ References

No definition available.

+ Details

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- Definition

Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
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-Section 50
-Paragraph 3
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+ Details

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Balance Type:	debit
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- Definition

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

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-Publisher FASB
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- Definition

Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in measure of progress which increases (decreases) right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

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-Publisher FASB
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Balance Type:	credit
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- Definition

Amount of decrease in right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time from transfer to receivable due to right to consideration becoming unconditional.

+ References

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- Definition

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

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Balance Type:	credit
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- Definition

Amount of revenue recognized from performance obligation satisfied or partially satisfied in previous reporting periods. Includes, but is not limited to, change in transaction price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

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-Name Accounting Standards Codification
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Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Revenue - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 14,196		$ 14,196	$ 13,504	$ 13,140
Percentage of total revenue		1.00%
Contract with customer, asset, additions			276
Contract with customer, asset, reclassified to receivable			263
Contract with customer, liability, revenue recognized			511
Performance obligation satisfied in previous period			47
Capitalized contract cost, amortization	217		775
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	364		$ 364	$ 364
Health Brokerage and Consulting
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer, percent			70.00%
Marsh Insurance Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, remaining performance obligation	29		$ 29
Mercer Consulting Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, remaining performance obligation	488		488
Oliver Wyman Group Consulting Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, remaining performance obligation	2		2
Deferred Implementation Costs
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Capitalized contract cost, net	41		41
Costs to Obtain
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Capitalized contract cost, net	203		203
Costs to Fulfill
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Capitalized contract cost, net	$ 160		$ 160