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Goodwill and Acquired Client Relationships - Schedule of Changes in Acquired Client Relationships (Details) - USD ($) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2020 | Jun. 30, 2020 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Definite-lived |  |  |  |  |
Foreign currency translation, accumulated depreciation |  |  | $ (600,000) | $ (3,700,000) |
Net Book Value |  |  |  |  |
Beginning balance, net book value |  |  | 1,048,800,000 |  |
Intangible amortization and impairments |  |  | (35,700,000) | (140,500,000) | $ (144,500,000)
Ending balance, net book value |  |  | 1,966,400,000 | 1,048,800,000 |
Acquired Client Relationships |  |  |  |  |
Definite-lived |  |  |  |  |
Beginning balance, gross book value |  |  | 1,166,600,000 | 1,248,800,000 |
Beginning balance, accumulated amortization |  |  | (1,026,800,000) | (1,039,000,000) |
Beginning balance, net book value |  |  | 139,800,000 | 209,800,000 |
Net investments |  |  | 232,000,000.0 |  |
Intangible amortization and impairments |  |  | (35,700,000) | (69,800,000) |
Foreign currency translation, gross book value |  |  | 600,000 | 3,500,000 |
Foreign currency translation, net book value |  |  | 0 | (200,000) |
Transfers, gross book value |  |  | (35,000,000.0) | (85,700,000) |
Transfers, accumulated amortization |  |  | 35,000,000.0 | 85,700,000 |
Ending balance, gross book value |  |  | 1,364,200,000 | 1,166,600,000 | 1,248,800,000
Ending balance, accumulated amortization |  |  | (1,028,100,000) | (1,026,800,000) | (1,039,000,000)
Ending balance, net book value |  |  | 336,100,000 | 139,800,000 | 209,800,000
Indefinite-lived |  |  |  |  |
Beginning balance, net book value |  |  | 909,000,000.0 | 972,200,000 |
Net investments |  |  | 725,000,000.0 |  |
Intangible impairments | $ (14,000,000) | $ (60,300,000) | 0 | (70,700,000) |
Foreign currency translation |  |  | (3,700,000) | 7,500,000 |
Ending balance, net book value |  |  | 1,630,300,000 | 909,000,000.0 | 972,200,000
Net Book Value |  |  |  |  |
Beginning balance, net book value |  |  | 1,048,800,000 | 1,182,000,000 |
New investments |  |  | 957,000,000.0 |  |
Intangible amortization and impairments |  |  | (35,700,000) | (140,500,000) |
Foreign currency translation |  |  | (3,700,000) | 7,300,000 |
Ending balance, net book value |  |  | $ 1,966,400,000 | $ 1,048,800,000 | $ 1,182,000,000

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