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Basis of Presentation and Accounting Policies - Additional Information (Details) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 USD ($) | Sep. 30, 2020 USD ($) | Dec. 31, 2020 USD ($)
Accounting Policies [Line Items] |  |  |
Non-cash impairment charge loss |  | $ 0 |
Goodwill | $ 1,215,000,000.0 |  | $ 1,225,800,000
United Kingdom |  |  |
Accounting Policies [Line Items] |  |  |
Percentage of goodwill over fair value of reporting unit | 12.00% |  |
United Kingdom | Discount Rates |  |  |
Accounting Policies [Line Items] |  |  |
Discount rate for goodwill impairment test (as a percent) | 11.5 |  |
United Kingdom | Terminal Value Revenue Growth Rate |  |  |
Accounting Policies [Line Items] |  |  |
Discount rate for goodwill impairment test (as a percent) | 1.0 |  |
United Kingdom | Terminal Value OUP Margin |  |  |
Accounting Policies [Line Items] |  |  |
Discount rate for goodwill impairment test (as a percent) | 3.1 |  |
Netherlands |  |  |
Accounting Policies [Line Items] |  |  |
Percentage of goodwill over fair value of reporting unit | 3.30% |  |
Netherlands | Discount Rates |  |  |
Accounting Policies [Line Items] |  |  |
Discount rate for goodwill impairment test (as a percent) | 10.9 |  |
Netherlands | Terminal Value Revenue Growth Rate |  |  |
Accounting Policies [Line Items] |  |  |
Discount rate for goodwill impairment test (as a percent) | 2.0 |  |
Netherlands | Terminal Value OUP Margin |  |  |
Accounting Policies [Line Items] |  |  |
Discount rate for goodwill impairment test (as a percent) | 3.5 |  |
Northern Europe | United Kingdom |  |  |
Accounting Policies [Line Items] |  |  |
Goodwill | $ 101,000,000.0 |  | 100,200,000
Northern Europe | Netherlands |  |  |
Accounting Policies [Line Items] |  |  |
Goodwill | $ 114,600,000 |  | $ 119,300,000
Minimum |  |  |
Accounting Policies [Line Items] |  |  |
Percentage of goodwill over fair value of reporting unit | 20.00% |  |
Minimum | Other Reporting Units |  |  |
Accounting Policies [Line Items] |  |  |
Percentage of goodwill over fair value of reporting unit | 20.00% |  |

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