Commitments and Contingencies - Schedule of Principal Debt Repayments (Parenthetical) (Detail) $ in Millions	Dec. 31, 2018 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Loan participations sold excluded from contractual obligations	$ 94.5
Non-consolidated senior interests excluded from contractual obligations	446.9
Securitized debt obligations excluded from contractual obligations	$ 1,300.0