Securitized Debt - Maturities of Long-Term Debt (Details) - Variable Interest Entities, Primary Beneficiary - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Securitized debt
Debt Instrument [Line Items]
Within One Year	$ 1,837,055	$ 1,582,646
One to Three Years	2,819,646	2,563,699
Three to Five Years	1,774,273	1,791,756
Greater Than Five Years	2,170,253	2,129,460
Total	8,601,227	8,067,561
Securitized Loans | Non-Agency RMBS
Debt Instrument [Line Items]
Within One Year	13,552	18,826
One to Three Years	11,229	18,332
Three to Five Years	1,589	4,453
Greater Than Five Years	305	665
Total	$ 26,675	$ 42,276