Consolidated Securitization Vehicles and Other Variable Interest Entities - Effect on Consolidated Results (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Variable Interest Entity [Line Items]
Net interest income	$ 116,666	$ 141,804	$ 274,850	$ 289,243
(Increase) decrease in provision for credit losses			(1,817)	0
Servicing fees	9,473	9,280	19,462	18,243
Variable Interest Entities, Primary Beneficiary
Variable Interest Entity [Line Items]
(Increase) decrease in provision for credit losses	75	0	(216)	0
Servicing fees	8,145	8,861	16,382	17,600
Variable Interest Entities, Primary Beneficiary | Non Agency Residential Mortgage Backed Securities And Securitized Loans
Variable Interest Entity [Line Items]
Interest income, Assets of consolidated VIEs	169,127	200,703	343,809	407,814
Interest expense, Non-recourse liabilities of VIEs	70,816	87,529	135,445	178,556
Net interest income	$ 98,311	$ 113,174	$ 208,364	$ 229,258