Significant Accounting Policies - Gain on Sale of Loans, Net (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Gains on sales of loans, net	$ 145,535	$ (10)	$ 3,679	$ 399,111	$ (247)	$ (4)	$ (369)	$ 238,935	$ 548,315	$ 238,315	$ 0
Proceeds from sale of loans receivable									4,240,000	3,100,000
Net proceeds from sales of loans held for investment, principal									3,980,000	2,900,000
Net proceeds from sales of loans held for investment, capitalized interest									$ 264,000	$ 199,000