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Equity Method Investments - Additional Information (Detail) - USD ($)	12 Months Ended
	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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