Securitized Debt Obligations, Net - Schedule of Information on Securitized Debt Obligations (Parenthetical) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Jan. 01, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019
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	$ 35.6	$ 11.9	$ 12.5	$ 36.9
Collateral Assets [Member] | Single Asset Securitization [Member]
Debt Instrument [Line Items]
Total loan amount, securitized		$ 500.0		$ 500.0