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Equity Method Investments - Additional Information (Detail) - USD ($) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Schedule Of Results Related To Equity Accounted Investees [Line Items] |  |  |
Undistributed earnings of equity method investees | $ 26,600,000 | $ 16,100,000 |
Reimbursable costs included in revenues of equity method investees | 3,851,500,000 | 3,516,100,000 | $ 5,339,700,000
Provision for income taxes | 82,976,000 | 69,065,000 | $ 52,840,000
Investees |  |  |
Schedule Of Results Related To Equity Accounted Investees [Line Items] |  |  |
Provision for income taxes | 0 |  |
Other Assets |  |  |
Schedule Of Results Related To Equity Accounted Investees [Line Items] |  |  |
Amounts due from related parties included in other assets | $ 2,500,000 | $ 2,600,000 |

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