Fair Value - Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financial assets not carried at fair value:
HTM debt securities	$ 704,691	$ 691,746
Financial liabilities not carried at fair value:
Unsecured senior notes	2,322,630	1,828,590
Carrying Value
Financial assets not carried at fair value:
Loans held-for-investment	16,197,636	15,477,624
HTM debt securities	701,306	683,136
Financial liabilities not carried at fair value:
Secured financing agreements, CLOs and SASB	15,329,466	15,192,966
Unsecured senior notes	2,322,630	1,828,590
Fair Value
Financial assets not carried at fair value:
Loans held-for-investment	16,204,044	15,526,235
HTM debt securities	673,999	656,864
Financial liabilities not carried at fair value:
Secured financing agreements, CLOs and SASB	15,356,458	15,266,440
Unsecured senior notes	$ 2,320,231	$ 1,893,065