Loans Held for Investment - By Region (Details)	Dec. 31, 2020	Dec. 31, 2019
Loans held for investment by Region [Line Items]
Percentage of Loans concentrated in major states	38.80%	39.40%
New York
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	9.70%	10.10%
California
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	9.60%	9.40%
Pennsylvania
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	8.00%	8.40%
New Jersey
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	6.20%	6.60%
Texas
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	5.30%	4.90%