Loans Held for Investment - By Region (Details)	Dec. 31, 2019	Dec. 31, 2018
Loans held for investment by Region [Line Items]
Percentage of Loans concentrated in major states	39.40%	39.90%
New York
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	10.10%	10.30%
California
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	9.40%	9.30%
Pennsylvania
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	8.40%	8.50%
New Jersey
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	6.60%	6.80%
Texas
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	4.90%
Illinois
Loans held for investment by Region [Line Items]
Percentage of Loans held in state		5.00%