Principles of Consolidation and Other Matters (Policies)	3 Months Ended
Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and Cash Equivalents	Cash and Cash EquivalentsCash and cash equivalents primarily consist of certificates of deposit and time deposits, with original maturities of three months or less, and money market funds. The estimated fair value of the Company's cash and cash equivalents approximates their carrying value. The Company is required to maintain operating funds primarily related to regulatory requirements outside of the U.S. or as collateral under captive insurance arrangements.
Allowance for Credit Losses on Accounts Receivable	Allowance for Credit Losses on Accounts ReceivableThe Company’s policy for providing an allowance for credit losses on its accounts receivable is based on a combination of factors, including historical write-offs, aging of balances, and other qualitative and quantitative analyses.
Investments	Investments The caption "Investment income" in the consolidated statements of income comprises realized and unrealized gains and losses from investments recognized in earnings. It includes, when applicable, other than temporary declines in the value of securities, mark-to-market increases or decreases in equity investments with readily determinable fair values and equity method gains or losses on the Company's investments in private equity funds. The Company holds investments in certain private equity funds. Investments in private equity funds are accounted for in accordance with the equity method of accounting using a consistently applied three-month lag period adjusted for any known significant changes from the lag period to the reporting date of the Company. The underlying private equity funds follow investment company accounting, where investments within the fund are carried at fair value. Investment gains or losses for its proportionate share of the change in fair value of the funds are recorded in earnings. Investments accounted for in accordance with the equity method of accounting are included in other assets in the consolidated balance sheets.
Income Taxes	Income Taxes The Company's effective tax rate for the three months ended March 31, 2023 was 24.7%, compared with 23.7% for the corresponding quarter of 2022. The tax rates in both periods reflect the impact of discrete tax items such as excess tax benefits related to share-based compensation, enacted tax legislation, changes in uncertain tax positions, deferred tax adjustments, nontaxable adjustments related to contingent consideration for acquisitions, and valuation allowances for certain tax credits and/or losses. The rate in the first quarter of 2023 reflects the previously enacted change in the U.K. corporate income tax rate from 19% to 25%, effective April 1, 2023. The blended U.K. statutory tax rate for 2023 is 23.5%. The excess tax benefit related to share-based payments is the most significant discrete item in both periods, reducing the effective tax rate by 1.3% and 1.8% for the three months ended March 31, 2023 and 2022, respectively. The Company's tax rate reflects its income, statutory tax rates, and tax planning in the various jurisdictions in which it operates. Significant judgment is required in determining the annual effective tax rate and in evaluating uncertain tax positions. Losses in one jurisdiction, generally, cannot offset earnings in another, and within certain jurisdictions profits and losses may not offset between entities. Consequently, losses in certain jurisdictions may require valuation allowances affecting the effective tax rate, depending on estimates of the realizability of associated deferred tax assets. The tax rate is also sensitive to changes in unrecognized tax benefits, including the impact of settled tax audits and expired statutes of limitations. The Company reports a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in tax returns. The Company's gross unrecognized tax benefits were $107 million at March 31, 2023, and $97 million at December 31, 2022. It is reasonably possible that the total amount of unrecognized tax benefits could decrease up to approximately $53 million within the next twelve months due to settlement of audits and expirations of statutes of limitations. Changes in tax laws, rulings, policies, or related legal and regulatory interpretations occur frequently and may have significant favorable or adverse impacts on our effective tax rate. On August 16, 2022, the Inflation Reduction Act of 2022 ("IRA") was enacted into law. The Company evaluated the provisions of the new legislation, the most significant of which are the corporate alternative minimum tax and the share repurchase tax. The IRA was effective as of January 1, 2023 and does not have a significant impact on the Company's financial results of operations for the current year.
Restructuring Costs	Restructuring Costs Charges associated with restructuring activities are recognized in accordance with applicable accounting guidance which includes accounting for disposal or exit activities, guidance related to impairment of ROU assets related to real estate leases, as well as other costs resulting from accelerated depreciation or amortization of leasehold improvements and other property and equipment. Severance and related costs are recognized based on amounts due under established severance plans or estimates of one-time benefits that will be provided. Typically, severance benefits are recognized when the impacted colleagues are notified of their expected termination and such termination is expected to occur within the legally required notification period. These costs are included in compensation and benefits in the consolidated statements of income. Costs for real estate consolidation are recognized based on the type of cost, and the expected future use of the facility. For locations where the Company does not expect to sub-lease the property, the amortization of any Right-of-use ("ROU") asset is accelerated from the decision date to the cease use date. For locations where the Company expects to sub-lease the properties subsequent to its vacating the property, the ROU asset is reviewed for potential impairment at the earlier of the cease use date or the date a sub-lease is signed. To determine the amount of impairment, the fair value of the ROU asset is determined based on the present value of the estimated net cash flows related to the property. Contractual costs outside of the ROU asset are recognized based on the net present value of expected future cash outflows for which the Company will not receive any benefit. Such amounts are reliant on estimates of future sub-lease income to be received and future contractual costs to be incurred. These costs are included in other operating expenses in the consolidated statements of income. Other costs related to restructuring, such as moving, legal or consulting costs are recognized as incurred. These costs are included in other operating expenses in the consolidated statements of income.
Foreign Currency	Foreign CurrencyThe financial statements of our international subsidiaries are translated from functional currency to U.S. dollars using month-end exchange rates for assets and liabilities, and average monthly exchange rates during the period for revenues and expenses. Translation adjustments are recorded in accumulated other comprehensive income (loss) ("AOCI") within the consolidated statements of equity. Foreign exchange transaction gains and losses resulting from the conversion of the transaction currency to functional currency are included in operating income in the consolidated statements of income.
Fair Value Measurement	Fair Value Hierarchy The Company has categorized its assets and liabilities that are valued at fair value on a recurring basis into a three-level fair value hierarchy as defined by the FASB. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets and liabilities (Level 1) and lowest priority to unobservable inputs (Level 3). In some cases, the inputs used to measure fair value might fall into different levels of the fair value hierarchy. In such cases, the level in the fair value hierarchy, for disclosure purposes, is determined based on the lowest level input that is significant to the fair value measurement. Assets and liabilities recorded in the consolidated balance sheets at fair value are categorized based on the inputs in the valuation techniques as follows: 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 are related to 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. Assets and liabilities measured using Level 3 inputs relate to assets and liabilities for contingent purchase consideration. Valuation Techniques Equity Securities, Money Market Funds and Mutual Funds – Level 1 Investments for which market quotations are readily available are valued at the sale price on their principal exchange or, for certain markets, official closing bid price. Money market funds are valued at a readily determinable price. Contingent Purchase Consideration Assets and Liabilities – Level 3 Purchase consideration for some acquisitions and dispositions made by the Company include contingent consideration arrangements. Contingent consideration arrangements are based primarily on EBITDA or revenue targets over a period of two to four years. The fair value of the contingent purchase consideration asset and liability is estimated as the present value of future cash flows to be paid, based on projections of revenue and earnings and related targets of the acquired and disposed entities.
New Accounting Guidance	New Accounting GuidanceNew Accounting Pronouncement Adopted Effective January 1, 2022:In October 2021, the FASB issued new guidance for measuring contract assets and contract liabilities acquired in a business combination. In accordance with the new guidance, contract assets and contract liabilities should be measured in accordance with the guidance for revenue from contracts with customers as opposed to the guidance for business combinations. The guidance must be applied on a prospective basis, and is effective for fiscal years beginning after December 15, 2022, including interim periods therein. Early adoption is permitted. The Company elected to adopt this new standard effective January 1, 2022. Adoption of this guidance did not have a material impact on the Company's financial position or results of operations.

Principles of Consolidation and Other Matters (Policies)

3 Months Ended

Mar. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Cash and Cash EquivalentsCash and cash equivalents primarily consist of certificates of deposit and time deposits, with original maturities of three months or less, and money market funds. The estimated fair value of the Company's cash and cash equivalents approximates their carrying value. The Company is required to maintain operating funds primarily related to regulatory requirements outside of the U.S. or as collateral under captive insurance arrangements.

Allowance for Credit Losses on Accounts Receivable

Allowance for Credit Losses on Accounts ReceivableThe Company’s policy for providing an allowance for credit losses on its accounts receivable is based on a combination of factors, including historical write-offs, aging of balances, and other qualitative and quantitative analyses.

Investments

The caption "Investment income" in the consolidated statements of income comprises realized and unrealized gains and losses from investments recognized in earnings. It includes, when applicable, other than temporary declines in the value of securities, mark-to-market increases or decreases in equity investments with readily determinable fair values and equity method gains or losses on the Company's investments in private equity funds.

The Company holds investments in certain private equity funds. Investments in private equity funds are accounted for in accordance with the equity method of accounting using a consistently applied three-month lag period adjusted for any known significant changes from the lag period to the reporting date of the Company. The underlying private equity funds follow investment company accounting, where investments within the fund are carried at fair value. Investment gains or losses for its proportionate share of the change in fair value of the funds are recorded in earnings. Investments accounted for in accordance with the equity method of accounting are included in other assets in the consolidated balance sheets.

Income Taxes

The Company's effective tax rate for the three months ended March 31, 2023 was 24.7%, compared with 23.7% for the corresponding quarter of 2022.

The tax rates in both periods reflect the impact of discrete tax items such as excess tax benefits related to share-based compensation, enacted tax legislation, changes in uncertain tax positions, deferred tax adjustments, nontaxable adjustments related to contingent consideration for acquisitions, and valuation allowances for certain tax credits and/or losses. The rate in the first quarter of 2023 reflects the previously enacted change in the U.K. corporate income tax rate from 19% to 25%, effective April 1, 2023. The blended U.K. statutory tax rate for 2023 is 23.5%.

The excess tax benefit related to share-based payments is the most significant discrete item in both periods, reducing the effective tax rate by 1.3% and 1.8% for the three months ended March 31, 2023 and 2022, respectively.

The Company's tax rate reflects its income, statutory tax rates, and tax planning in the various jurisdictions in which it operates. Significant judgment is required in determining the annual effective tax rate and in evaluating uncertain tax positions.

Losses in one jurisdiction, generally, cannot offset earnings in another, and within certain jurisdictions profits and losses may not offset between entities. Consequently, losses in certain jurisdictions may require valuation allowances affecting the effective tax rate, depending on estimates of the realizability of associated deferred tax assets. The tax rate is also sensitive to changes in unrecognized tax benefits, including the impact of settled tax audits and expired statutes of limitations.

The Company reports a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in tax returns. The Company's gross unrecognized tax benefits were $107 million at March 31, 2023, and $97 million at December 31, 2022. It is reasonably possible that the total amount of unrecognized tax benefits could decrease up to approximately $53 million within the next twelve months due to settlement of audits and expirations of statutes of limitations.

Changes in tax laws, rulings, policies, or related legal and regulatory interpretations occur frequently and may have significant favorable or adverse impacts on our effective tax rate.

On August 16, 2022, the Inflation Reduction Act of 2022 ("IRA") was enacted into law. The Company evaluated the provisions of the new legislation, the most significant of which are the corporate alternative minimum tax and the share repurchase tax. The IRA was effective as of January 1, 2023 and does not have a significant impact on the Company's financial results of operations for the current year.

Restructuring Costs

Charges associated with restructuring activities are recognized in accordance with applicable accounting guidance which includes accounting for disposal or exit activities, guidance related to impairment of ROU assets related to real estate leases, as well as other costs resulting from accelerated depreciation or amortization of leasehold improvements and other property and equipment.

Severance and related costs are recognized based on amounts due under established severance plans or estimates of one-time benefits that will be provided. Typically, severance benefits are recognized when the impacted colleagues are notified of their expected termination and such termination is expected to occur within the legally required notification period. These costs are included in compensation and benefits in the consolidated statements of income.

Costs for real estate consolidation are recognized based on the type of cost, and the expected future use of the facility. For locations where the Company does not expect to sub-lease the property, the amortization of any Right-of-use ("ROU") asset is accelerated from the decision date to the cease use date. For locations where the Company expects to sub-lease the properties subsequent to its vacating the property, the ROU asset is reviewed for potential impairment at the earlier of the cease use date or the date a sub-lease is signed. To determine the amount of impairment, the fair value of the ROU asset is determined based on the present value of the estimated net cash flows related to the property. Contractual costs outside of the ROU asset are recognized based on the net present value of expected future cash outflows for which the Company will not receive any benefit. Such amounts are reliant on estimates of future sub-lease income to be received and future contractual costs to be incurred. These costs are included in other operating expenses in the consolidated statements of income.

Other costs related to restructuring, such as moving, legal or consulting costs are recognized as incurred. These costs are included in other operating expenses in the consolidated statements of income.

Foreign Currency

Foreign CurrencyThe financial statements of our international subsidiaries are translated from functional currency to U.S. dollars using month-end exchange rates for assets and liabilities, and average monthly exchange rates during the period for revenues and expenses. Translation adjustments are recorded in accumulated other comprehensive income (loss) ("AOCI") within the consolidated statements of equity. Foreign exchange transaction gains and losses resulting from the conversion of the transaction currency to functional currency are included in operating income in the consolidated statements of income.

Fair Value Measurement

Fair Value Hierarchy

The Company has categorized its assets and liabilities that are valued at fair value on a recurring basis into a three-level fair value hierarchy as defined by the FASB. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets and liabilities (Level 1) and lowest priority to unobservable inputs (Level 3). In some cases, the inputs used to measure fair value might fall into different levels of the fair value hierarchy. In such cases, the level in the fair value hierarchy, for disclosure purposes, is determined based on the lowest level input that is significant to the fair value measurement. Assets and liabilities recorded in the consolidated balance sheets at fair value are categorized based on the inputs in the valuation techniques as follows:

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 are related to 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.

Assets and liabilities measured using Level 3 inputs relate to assets and liabilities for contingent purchase consideration.

Valuation Techniques

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

Investments for which market quotations are readily available are valued at the sale price on their principal exchange or, for certain markets, official closing bid price. Money market funds are valued at a readily determinable price.

Contingent Purchase Consideration Assets and Liabilities – Level 3

Purchase consideration for some acquisitions and dispositions made by the Company include contingent consideration arrangements. Contingent consideration arrangements are based primarily on EBITDA or revenue targets over a period of two to four years. The fair value of the contingent purchase consideration asset and liability is estimated as the present value of future cash flows to be paid, based on projections of revenue and earnings and related targets of the acquired and disposed entities.

New Accounting Guidance

New Accounting GuidanceNew Accounting Pronouncement Adopted Effective January 1, 2022:In October 2021, the FASB issued new guidance for measuring contract assets and contract liabilities acquired in a business combination. In accordance with the new guidance, contract assets and contract liabilities should be measured in accordance with the guidance for revenue from contracts with customers as opposed to the guidance for business combinations. The guidance must be applied on a prospective basis, and is effective for fiscal years beginning after December 15, 2022, including interim periods therein. Early adoption is permitted. The Company elected to adopt this new standard effective January 1, 2022. Adoption of this guidance did not have a material impact on the Company's financial position or results of operations.

- Definition

Disclosure of accounting policy for credit loss on financial instrument measured at amortized cost basis, net investment in lease, off-balance sheet credit exposure, and available-for-sale debt security. Includes, but is not limited to, methodology used to estimate allowance for credit loss, how writeoff of uncollectible amount is recognized, and determination of past due status and nonaccrual status.

+ References

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+ Details

- Definition

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.

+ References + Details