Securitized Debt Obligations, Net - Schedule of Information on Securitized Debt Obligations (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Debt Instrument [Line Items]
Percentage of loans financed by securitized debt obligations earned floating rate of interest			98.00%
Interest expense on securitized debt obligations	$ 12.5	$ 12.0	$ 25.0	$ 23.1
Collateral Assets [Member] | Single Asset Securitization [Member]
Debt Instrument [Line Items]
Total loan amount, securitized	$ 500.0		$ 500.0