Basis of Presentation and Recent Accounting Pronouncements (Policies)	6 Months Ended
Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited quarterly condensed consolidated financial statements of Willis Towers Watson and our subsidiaries are presented in accordance with the rules and regulations of the SEC for quarterly reports on Form 10-Q and therefore do not include all of the information and footnotes required by U.S. GAAP. In the opinion of management, these condensed consolidated financial statements reflect all adjustments, consisting of normal recurring adjustments, which are necessary for a fair presentation of the condensed consolidated financial statements and results for the interim periods. All intercompany accounts and transactions have been eliminated in consolidation. The condensed consolidated financial statements should be read together with the Company’s Annual Report on Form 10-K, filed with the SEC on February 26, 2020, and may be accessed via EDGAR on the SEC’s web site at www.sec.gov. The results of operations for the three and six months ended June 30, 2020 are not necessarily indicative of the results that can be expected for the entire year. The Company experiences seasonal fluctuations of its revenue. Revenue is typically higher during the Company’s first and fourth quarters due primarily to the timing of broking-related activities. The results reflect certain estimates and assumptions made by management, including those estimates used in calculating acquisition consideration and fair value of tangible and intangible assets and liabilities, professional liability claims, estimated bonuses, valuation of billed and unbilled receivables, and anticipated tax liabilities that affect the amounts reported in the condensed consolidated financial statements and related notes.
Risks and Uncertainties Related to the COVID-19 Pandemic	Risks and Uncertainties Related to the COVID-19 Pandemic The COVID-19 pandemic has had an adverse impact on global commercial activity, including the global supply chain, and has contributed to significant volatility in the financial markets including, among other effects, occasional declines in the equity markets, changes in interest rates and reduced liquidity on a global basis. In light of the effects on our own business operations and those of our clients, suppliers and other third parties with whom we interact, the Company has considered the impact of COVID-19 on our business. This analysis takes into account our business resilience and continuity plans, financial modeling and stress testing of liquidity and financial resources. The analysis concluded that the COVID-19 pandemic did not have a material adverse impact to our financial results for the first quarter of 2020; however, we expected that the impact of COVID-19 on general economic activity could negatively impact our revenue and operating results for the remainder of 2020. During the second quarter of 2020, the COVID-19 pandemic had a negative impact on revenue growth, particularly in our businesses that are discretionary in nature, but otherwise it generally had no material impact on our overall results. Some of our discretionary, project-based businesses saw a reduction in demand, and potential negative impacts on our revenue and operating results may lag behind the developments thus far related to the COVID-19 pandemic. Also, the increased frequency and severity of coverage disputes between our clients and (re)insurers arising out of the pandemic could increase our professional liability risk. We will continue to monitor the situation and assess possible implications to our business and our stakeholders. The extent to which COVID-19 impacts our business and financial position will depend on future developments, which are difficult to predict. These future developments may include the severity and scope of the COVID-19 outbreak, which may unexpectedly change or worsen, and the types and duration of measures imposed by governmental authorities to contain the virus or address its impact. We continue to expect that the COVID-19 pandemic will negatively impact our revenue and operating results for the remainder of 2020 and potentially beyond. The Company has considered multiple scenarios, with both positive and negative inputs, as part of the significant estimates and assumptions that are inherent in our financial statements. These inputs are based on trends in client behavior and the economic environment throughout the first half of 2020 as COVID-19 has moved throughout the geographies in which we operate. These estimates and assumptions include the collectability of billed and unbilled receivables, the estimation of revenue, and the fair value of our reporting units, tangible and intangible assets and contingent consideration. With regard to collectability, the Company believes it may face atypical delays in client payments going forward. In addition, we believe that the demand for certain discretionary lines of business has decreased, and that such decrease will impact our financial results in succeeding periods. Non-discretionary lines of business may also be adversely affected, for example because reduced economic activity or disruption in insurance markets reduces demand for or the extent of insurance coverage. We believe that these trends and uncertainties are comparable to those faced by other registrants as a result of the pandemic. CARES Act On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security (‘CARES’) Act was enacted in the U.S. to provide relief to companies in the midst of the COVID-19 pandemic and to stimulate the economy. The assistance includes temporary tax relief and government loans, grants and investments for entities in affected industries. With regard to the income tax provisions of the CARES Act, the Company has reviewed its eligibility requirements, including if and how they apply and how they will affect the Company, particularly provisions that (i) eliminate the taxable income limit for certain net operating losses (‘NOLs’) and allow businesses to carry back NOLs arising in 2018, 2019 and 2020 to the five prior tax years; (ii) generally relaxed the business interest limitation under section 163(j) from 30 percent to 50 percent; and (iii) fix the ‘retail glitch’ for qualified improvement property. During the three months ended June 30, 2020, the Company elected to use the section 163(j) 50 percent business interest limitation for tax years 2019 and 2020. Utilizing this temporary provision, the Company accelerated a cash tax benefit in 2020 of approximately $40 million for tax years 2019 and 2020. Moreover, the Company will recognize tax expense of approximately $25 million and $22 million for the 2019 and 2020 tax years, respectively, primarily related to an incremental Base Erosion and Anti-Abuse Tax (‘BEAT’). During the quarter, the Company recorded tax expense of $35 million relating to the 2019 and 2020 tax years, and expects to recognize the remaining $12 million BEAT expense during the remainder of 2020. Additionally, the CARES Act offers an employee retention credit to encourage employers to maintain headcounts even if employees cannot report to work because of issues related to COVID-19 as well as a temporary provision allowing companies to defer remitting the employer share of some payroll taxes to the government. The payroll tax provisions of the CARES Act were not material for the six months ended June 30, 2020 and are currently not expected to be material for calendar year 2020.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Not Yet Adopted In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes, which clarifies and amends existing guidance, including removing certain exceptions to the general principles of accounting for income taxes. This ASU becomes effective for the Company on January 1, 2021. Some of the changes must be applied on a retrospective or modified retrospective basis while others must be applied on a prospective basis. Early adoption is permitted. The Company does not plan to adopt this ASU early and is assessing the expected impact on our condensed consolidated financial statements. Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments, which amended the guidance on the impairment of financial instruments. The ASU added an impairment model (known as the current expected credit loss (‘CECL’) model) that is based on expected losses rather than incurred losses. Under the new guidance, an entity recognizes as an allowance its estimate of lifetime expected credit losses on assets measured at amortized cost, which is intended to result in more timely recognition of such losses. The ASU was also intended to reduce the complexity of U.S. GAAP by decreasing the number of credit impairment models that entities use to account for debt instruments. Further, the ASU made targeted changes to the impairment model for available-for-sale debt securities. Additional ASUs were subsequently issued which provided amended and additional guidance for the implementation of ASU No. 2016-13. All related guidance has been codified into, and is now known as, ASC 326, Financial Instruments—Credit Losses (‘ASC 326’). ASC 326 became effective for the Company on January 1, 2020, at which time we adopted it. This ASU did not have a material impact on our condensed consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment, which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. In computing the implied fair value of goodwill under Step 2, previous U.S. GAAP required the performance of procedures to determine the fair value at the impairment testing date of assets and liabilities (including unrecognized assets and liabilities) following the procedure that is required in determining the fair value of assets acquired and liabilities assumed in a business combination. Instead, the amendments under this ASU require the goodwill impairment test to be performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge would be recognized for 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. The ASU became effective for the Company on January 1, 2020, at which time we adopted it. The amendments in this ASU are applied on a prospective basis. There is no immediate impact to our condensed consolidated financial statements upon adopting this ASU, until such time as the next goodwill impairment test is performed (October 1, 2020, or sooner should circumstances warrant it). The most recent Step 1 goodwill impairment test resulted in fair values in excess of carrying values for all reporting units at October 1, 2019. In August 2018, the FASB issued ASU 2018-13, Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement as part of its disclosure framework project. The focus of this project is to improve the effectiveness of disclosures in the notes to the financial statements by facilitating clear communication of the information required by U.S. GAAP that is most important to users of an entity’s financial statements. This ASU removes certain disclosure requirements and adds or modifies other requirements. This ASU was effective for the Company on January 1, 2020, at which time we adopted it. Certain provisions of the ASU were required to be adopted retrospectively, while others were required to be adopted prospectively. This ASU did not have a material impact on the notes to our condensed consolidated financial statements. In March 2020, the SEC issued a final rule that amends the disclosure requirements related to certain registered securities under SEC Regulation S-X, Rules 3-10 and 3-16 which currently require separate financial statements for subsidiary issuers and guarantors of registered debt securities unless certain exceptions are met, and affiliates that collateralize registered securities offerings if the affiliates’ securities are a substantial portion of the collateral. The final rule is generally effective for filings on or after January 4, 2021, however early application is permitted. The most pertinent portions of the final rule that are currently applicable to the Company include: (i) replacing the previous requirement under Rule 3-10 to provide condensed consolidating financial information in the registrant’s financial statements with a requirement to provide alternative financial disclosures (which include summarized financial information of the parent and any issuers and guarantors, as well as other qualitative disclosures) in either the registrant’s Management’s Discussion & Analysis section or its financial statements; and, (ii) reducing the periods for which summarized financial information is required to the most recent annual period and year-to-date interim period. The Company elected to early-adopt the provisions of the final rule during the three months ended March 31, 2020. Further, the new reduced quantitative disclosures and accompanying qualitative disclosures as required by this final rule are in Item II, Management’s Discussion and Analysis of Financial Condition and Results of Operations on this Form 10-Q. In March 2020, the FASB issued ASU No. 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting, which provides optional expedients and exceptions for accounting for contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The amendments apply only to contracts, hedging relationships and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. This ASU became effective for the Company on March 12, 2020. The Company may apply the changes relating to contracts from January 1, 2020 or from a later date. The Company has made no contract modifications thus far to transition to a different reference rate, however it will consider this guidance as future modifications are made.

Basis of Presentation and Recent Accounting Pronouncements (Policies)

6 Months Ended

Jun. 30, 2020

The accompanying unaudited quarterly condensed consolidated financial statements of Willis Towers Watson and our subsidiaries are presented in accordance with the rules and regulations of the SEC for quarterly reports on Form 10-Q and therefore do not include all of the information and footnotes required by U.S. GAAP. In the opinion of management, these condensed consolidated financial statements reflect all adjustments, consisting of normal recurring adjustments, which are necessary for a fair presentation of the condensed consolidated financial statements and results for the interim periods. All intercompany accounts and transactions have been eliminated in consolidation. The condensed consolidated financial statements should be read together with the Company’s Annual Report on Form 10-K, filed with the SEC on February 26, 2020, and may be accessed via EDGAR on the SEC’s web site at www.sec.gov.

The results of operations for the three and six months ended June 30, 2020 are not necessarily indicative of the results that can be expected for the entire year. The Company experiences seasonal fluctuations of its revenue. Revenue is typically higher during the Company’s first and fourth quarters due primarily to the timing of broking-related activities. The results reflect certain estimates and assumptions made by management, including those estimates used in calculating acquisition consideration and fair value of tangible and intangible assets and liabilities, professional liability claims, estimated bonuses, valuation of billed and unbilled receivables, and anticipated tax liabilities that affect the amounts reported in the condensed consolidated financial statements and related notes.

Risks and Uncertainties Related to the COVID-19 Pandemic

The COVID-19 pandemic has had an adverse impact on global commercial activity, including the global supply chain, and has contributed to significant volatility in the financial markets including, among other effects, occasional declines in the equity markets, changes in interest rates and reduced liquidity on a global basis. In light of the effects on our own business operations and those of our clients, suppliers and other third parties with whom we interact, the Company has considered the impact of COVID-19 on our business. This analysis takes into account our business resilience and continuity plans, financial modeling and stress testing of liquidity and financial resources.

The analysis concluded that the COVID-19 pandemic did not have a material adverse impact to our financial results for the first quarter of 2020; however, we expected that the impact of COVID-19 on general economic activity could negatively impact our revenue and operating results for the remainder of 2020. During the second quarter of 2020, the COVID-19 pandemic had a negative impact on revenue growth, particularly in our businesses that are discretionary in nature, but otherwise it generally had no material impact on our overall results. Some of our discretionary, project-based businesses saw a reduction in demand, and potential negative impacts on our revenue and operating results may lag behind the developments thus far related to the COVID-19 pandemic. Also, the increased frequency and severity of coverage disputes between our clients and (re)insurers arising out of the pandemic could increase our professional liability risk. We will continue to monitor the situation and assess possible implications to our business and our stakeholders. The extent to which COVID-19 impacts our business and financial position will depend on future developments, which are difficult to predict. These future developments may include the severity and scope of the COVID-19 outbreak, which may unexpectedly change or worsen, and the types and duration of measures imposed by governmental authorities to contain the virus or address its impact. We continue to expect that the COVID-19 pandemic will negatively impact our revenue and operating results for the remainder of 2020 and potentially beyond.

The Company has considered multiple scenarios, with both positive and negative inputs, as part of the significant estimates and assumptions that are inherent in our financial statements. These inputs are based on trends in client behavior and the economic environment throughout the first half of 2020 as COVID-19 has moved throughout the geographies in which we operate. These estimates and assumptions include the collectability of billed and unbilled receivables, the estimation of revenue, and the fair value of our reporting units, tangible and intangible assets and contingent consideration. With regard to collectability, the Company believes it may face atypical delays in client payments going forward. In addition, we believe that the demand for certain discretionary lines of business has decreased, and that such decrease will impact our financial results in succeeding periods. Non-discretionary lines of business may also be adversely affected, for example because reduced economic activity or disruption in insurance markets reduces demand for or the extent of insurance coverage. We believe that these trends and uncertainties are comparable to those faced by other registrants as a result of the pandemic.

CARES Act

On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security (‘CARES’) Act was enacted in the U.S. to provide relief to companies in the midst of the COVID-19 pandemic and to stimulate the economy. The assistance includes temporary tax relief and government loans, grants and investments for entities in affected industries.

With regard to the income tax provisions of the CARES Act, the Company has reviewed its eligibility requirements, including if and how they apply and how they will affect the Company, particularly provisions that (i) eliminate the taxable income limit for certain net operating losses (‘NOLs’) and allow businesses to carry back NOLs arising in 2018, 2019 and 2020 to the five prior tax years; (ii) generally relaxed the business interest limitation under section 163(j) from 30 percent to 50 percent; and (iii) fix the ‘retail glitch’ for qualified improvement property.

During the three months ended June 30, 2020, the Company elected to use the section 163(j) 50 percent business interest limitation for tax years 2019 and 2020. Utilizing this temporary provision, the Company accelerated a cash tax benefit in 2020 of approximately $40 million for tax years 2019 and 2020. Moreover, the Company will recognize tax expense of approximately $25 million and $22 million for the 2019 and 2020 tax years, respectively, primarily related to an incremental Base Erosion and Anti-Abuse Tax (‘BEAT’). During the quarter, the Company recorded tax expense of $35 million relating to the 2019 and 2020 tax years, and expects to recognize the remaining $12 million BEAT expense during the remainder of 2020.

Additionally, the CARES Act offers an employee retention credit to encourage employers to maintain headcounts even if employees cannot report to work because of issues related to COVID-19 as well as a temporary provision allowing companies to defer remitting the employer share of some payroll taxes to the government. The payroll tax provisions of the CARES Act were not material for the six months ended June 30, 2020 and are currently not expected to be material for calendar year 2020.

Recent Accounting Pronouncements

Not Yet Adopted

In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes, which clarifies and amends existing guidance, including removing certain exceptions to the general principles of accounting for income taxes. This ASU becomes effective for the Company on January 1, 2021. Some of the changes must be applied on a retrospective or modified retrospective basis while others must be applied on a prospective basis. Early adoption is permitted. The Company does not plan to adopt this ASU early and is assessing the expected impact on our condensed consolidated financial statements.

Adopted

In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments, which amended the guidance on the impairment of financial instruments. The ASU added an impairment model (known as the current expected credit loss (‘CECL’) model) that is based on expected losses rather than incurred losses. Under the new guidance, an entity recognizes as an allowance its estimate of lifetime expected credit losses on assets measured at amortized cost, which is intended to result in more timely recognition of such losses. The ASU was also intended to reduce the complexity of U.S. GAAP by decreasing the number of credit impairment models that entities use to account for debt instruments. Further, the ASU made targeted changes to the impairment model for available-for-sale debt securities. Additional ASUs were subsequently issued which provided amended and additional guidance for the implementation of ASU No. 2016-13. All related guidance has been codified into, and is now known as, ASC 326, Financial Instruments—Credit Losses (‘ASC 326’). ASC 326 became effective for the Company on January 1, 2020, at which time we adopted it. This ASU did not have a material impact on our condensed consolidated financial statements.

In January 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment, which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. In computing the implied fair value of goodwill under Step 2, previous U.S. GAAP required the performance of procedures to determine the fair value at the impairment testing date of assets and liabilities (including unrecognized assets and liabilities) following the procedure that is required in determining the fair value of assets acquired and liabilities assumed in a business combination. Instead, the amendments under this ASU require the goodwill impairment test to be performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge would be recognized for 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. The ASU became effective for the Company on January 1, 2020, at which time we adopted it. The amendments in this ASU are applied on a prospective basis. There is no immediate impact to our condensed consolidated financial statements upon adopting this ASU, until such time as the next goodwill impairment test is performed (October 1, 2020, or sooner should circumstances warrant it). The most recent Step 1 goodwill impairment test resulted in fair values in excess of carrying values for all reporting units at October 1, 2019.

In August 2018, the FASB issued ASU 2018-13, Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement as part of its disclosure framework project. The focus of this project is to improve the effectiveness of disclosures in the notes to the financial statements by facilitating clear communication of the information required by U.S. GAAP that is most important to users of an entity’s financial statements. This ASU removes certain disclosure requirements and adds or modifies other requirements. This ASU was effective for the Company on January 1, 2020, at which time we adopted it. Certain provisions of the ASU were required to be adopted retrospectively, while others were required to be adopted prospectively. This ASU did not have a material impact on the notes to our condensed consolidated financial statements.

In March 2020, the SEC issued a final rule that amends the disclosure requirements related to certain registered securities under SEC Regulation S-X, Rules 3-10 and 3-16 which currently require separate financial statements for subsidiary issuers and guarantors of registered debt securities unless certain exceptions are met, and affiliates that collateralize registered securities offerings if the affiliates’ securities are a substantial portion of the collateral. The final rule is generally effective for filings on or after January 4, 2021, however early application is permitted. The most pertinent portions of the final rule that are currently applicable to the Company include: (i) replacing the previous requirement under Rule 3-10 to provide condensed consolidating financial information in the registrant’s financial statements with a requirement to provide alternative financial disclosures (which include summarized financial information of the parent and any issuers and guarantors, as well as other qualitative disclosures) in either the registrant’s Management’s Discussion & Analysis section or its financial statements; and, (ii) reducing the periods for which summarized financial information is required to the most recent annual period and year-to-date interim period. The Company elected to early-adopt the provisions of the final rule during the three months ended March 31, 2020. Further, the new reduced quantitative disclosures and accompanying qualitative disclosures as required by this final rule are in Item II, Management’s Discussion and Analysis of Financial Condition and Results of Operations on this Form 10-Q.

In March 2020, the FASB issued ASU No. 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting, which provides optional expedients and exceptions for accounting for contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The amendments apply only to contracts, hedging relationships and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. This ASU

became effective for the Company on March 12, 2020. The Company may apply the changes relating to contracts from January 1, 2020 or from a later date. The Company has made no contract modifications thus far to transition to a different reference rate, however it will consider this guidance as future modifications are made.