Significant Accounting Policies - Gain on Sale of Loans, Net (Details) - USD ($) $ in Thousands	3 Months Ended					12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gains on sales of loans, net	$ (247)	$ (4)	$ (369)	$ 238,935		$ 238,315	$ 0	$ 2,060
Proceeds from sale of loans receivable				3,100,000
Net proceeds from sales of loans held for investment, principal				2,900,000
Net proceeds from sales of loans held for investment, capitalized interest				199,000
Net proceeds from sales of loans held for investment, accrued interest				12,000
Discontinued Operations, Disposed of by Sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Split Loans portfolio sales price				$ 43,000	$ 43,000
Gains on sales of loans, net					$ 2,000