Commitments and Contingencies - Schedule of Principal Debt Repayments (Parenthetical) (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($)
Debt Instrument [Line Items]
Debt Instrument Amortization Percentage	1.00%
Securitized debt obligations excluded from contractual obligations	$ 2,900.0
Non-consolidated securitized debt excluded from contractual obligations	997.6
Non-consolidated senior interests excluded from contractual obligations	$ 414.1