Securitized Debt - Maturities (Detail) - Variable Interest Entities, Primary Beneficiary, Aggregated Disclosure - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Securitized debt
Debt Instrument [Line Items]
Within One Year	$ 1,647,041	$ 1,582,646
One to Three Years	2,663,326	2,563,699
Three to Five Years	1,815,521	1,791,756
Greater Than Five Years	2,290,166	2,129,460
Total	8,416,054	8,067,561
Securitized Loans | Non-Agency RMBS
Debt Instrument [Line Items]
Within One Year	15,131	18,826
One to Three Years	16,149	18,332
Three to Five Years	5,056	4,453
Greater Than Five Years	461	665
Total	$ 36,797	$ 42,276