Loans Held-for-Investment by Geographic Location (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value	$ 3,978,862	$ 4,226,212
Percentage of Loan Portfolio	100.00%	100.00%
United States, Northeastern Region
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value	$ 1,065,128	$ 1,196,767
Percentage of Loan Portfolio	26.80%	28.40%
United States, Southwestern Region
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value	$ 818,056	$ 923,519
Percentage of Loan Portfolio	20.50%	21.80%
United States, Western Region
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value	$ 723,076	$ 735,416
Percentage of Loan Portfolio	18.20%	17.40%
United States, Midwestern Region
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value	$ 714,628	$ 700,778
Percentage of Loan Portfolio	18.00%	16.60%
United States, Southeastern Region
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value	$ 657,974	$ 669,732
Percentage of Loan Portfolio	16.50%	15.80%