Principles of Consolidation and Other Matters	3 Months Ended
Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Principles of Consolidation and Other Matters	Principles of Consolidation and Other Matters The Company prepared the consolidated financial statements included herein pursuant to the rules and regulations of the Securities and Exchange Commission. For interim filings, certain information and disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been omitted pursuant to such rules and regulations. The Company believes that the information and disclosures presented are adequate to make such information and disclosures not misleading. These consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 (the "2020 Form 10-K"). The financial information contained herein reflects all normal recurring adjustments which are, in the opinion of management, necessary for a fair presentation of the Company’s consolidated financial statements as of and for the three month periods ended March 31, 2021 and 2020. Estimates: The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. On an ongoing basis, the Company evaluates its estimates, judgments and methodologies. The estimates are based on historical experience and on various other assumptions that the Company believes are reasonable. Such matters include: •the allowance for current expected credit losses on receivables, •estimates of revenue, •impairment assessments and charges, •recoverability of long-lived assets, •liabilities for errors and omissions, •deferred tax assets, uncertain tax positions and income tax expense, •share-based and incentive compensation expense, •useful lives assigned to long-lived assets, and depreciation and amortization, •fair value estimates of contingent consideration receivable or payable related to acquisitions or dispositions The Company believes these estimates are reasonable based on information currently available at the time they are made. The Company also considered any COVID-19 potential impacts to its customer base in various industries and geographies and has concluded through March 31, 2021, that COVID-19 did not have a material adverse impact on the Company's financial position or estimates. The ultimate extent to which COVID-19 will directly or indirectly impact the Company’s businesses, results of operations and financial condition will depend on numerous evolving factors and future developments that it is not able to predict. Actual results may differ from these estimates. Cash and Cash Equivalents Cash 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 United States or as collateral under captive insurance arrangements. At March 31, 2021, the Company maintained $272 million compared to $270 million at December 31, 2020 related to these regulatory requirements. Allowance for Credit Losses on Accounts Receivable The 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. The charge related to expected credit losses was immaterial to the consolidated statement of income for the three months ended March 31, 2021. Investments The caption "Investment income (loss)" 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 that 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 the Company's proportionate share of the change in fair value of the funds are recorded in earnings. Investments accounted for using the equity method of accounting are included in "other assets" in the consolidated balance sheets. The Company recorded net investment income of $11 million for the three months ended March 31, 2021 compared to a net investment loss of $2 million for the same period last year. The increase is primarily due to gains from its investments in private equity funds. Income Taxes The Company's effective tax rate in the first quarter of 2021 was 24.5% compared with 23.8% in the first quarter of 2020. 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 and nontaxable adjustments to contingent acquisition consideration. The excess tax benefit related to share-based payments is the most significant discrete item, reducing the effective tax rate by 1.1% and 2.6% in the first quarters of 2021 and 2020, 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 limitation. Changes in tax laws or tax rulings may have a significant impact on our effective tax rate. 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 was $96 million at March 31, 2021 and $98 million at December 31, 2020. It is reasonably possible that the total amount of unrecognized tax benefits will decrease between zero and approximately $35 million within the next twelve months due to settlements of audits and expirations of statutes of limitation. Integration and Restructuring Charges 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 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 right-of-use 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 right-of-use asset is determined based on the present value of the estimated net cash flows related to the property. Contractual costs outside of the right-of-use 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 based 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 integration and 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.

The Company prepared the consolidated financial statements included herein pursuant to the rules and regulations of the Securities and Exchange Commission. For interim filings, certain information and disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been omitted pursuant to such rules and regulations. The Company believes that the information and disclosures presented are adequate to make such information and disclosures not misleading. These consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 (the "2020 Form 10-K").

The financial information contained herein reflects all normal recurring adjustments which are, in the opinion of management, necessary for a fair presentation of the Company’s consolidated financial statements as of and for the three month periods ended March 31, 2021 and 2020.

Estimates: The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. On an ongoing basis, the Company evaluates its estimates, judgments and methodologies. The estimates are based on historical experience and on various other assumptions that the Company believes are reasonable. Such matters include:

The Company believes these estimates are reasonable based on information currently available at the time they are made. The Company also considered any COVID-19 potential impacts to its customer base in various industries and geographies and has concluded through March 31, 2021, that COVID-19 did not have a material adverse impact on the Company's financial position or estimates. The ultimate extent to which COVID-19 will directly or indirectly impact the Company’s businesses, results of operations and financial condition will depend on numerous evolving factors and future developments that it is not able to predict. Actual results may differ from these estimates.

Cash 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 United States or as collateral under captive insurance arrangements. At March 31, 2021, the Company maintained $272 million compared to $270 million at December 31, 2020 related to these regulatory requirements.

The 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. The charge related to expected credit losses was immaterial to the consolidated statement of income for the three months ended March 31, 2021.

The caption "Investment income (loss)" 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 that 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 the Company's proportionate share of the change in fair value of the funds are recorded in earnings. Investments accounted for using the equity method of accounting are included in "other assets" in the consolidated balance sheets.

The Company recorded net investment income of $11 million for the three months ended March 31, 2021 compared to a net investment loss of $2 million for the same period last year. The increase is primarily due to gains from its investments in private equity funds.

The Company's effective tax rate in the first quarter of 2021 was 24.5% compared with 23.8% in the first quarter of 2020. 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 and nontaxable adjustments to contingent acquisition consideration. The excess tax benefit related to share-based payments is the most significant discrete item, reducing the effective tax rate by 1.1% and 2.6% in the first quarters of 2021 and 2020, 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 limitation.

Changes in tax laws or tax rulings may have a significant impact on our effective tax rate. 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 was $96 million at March 31, 2021 and $98 million at December 31, 2020. It is reasonably possible that the total amount of unrecognized tax benefits will decrease between zero and approximately $35 million within the next twelve months due to settlements of audits and expirations of statutes of limitation.

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 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 right-of-use 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 right-of-use asset is determined based on the present value of the estimated net cash flows related to the property. Contractual costs outside of the right-of-use 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 based on estimates of future sub-lease income to be received and future contractual costs to be incurred.

Other costs related to integration and 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.