Commercial Mortgage Loans Held for Investment - Additional Information (Details) |
3 Months Ended | 12 Months Ended |
---|---|---|
Mar. 31, 2019
USD ($)
Loan
Rating
|
Dec. 31, 2018
USD ($)
Loan
Rating
|
|
Mortgage Loans On Real Estate [Abstract] | ||
Weighted average risk rating | Rating | 2 | 2 |
Allowance for loan losses | $ | $ 0 | $ 0 |
Number of loans risk rated two | 20 | 17 |
Number of loans risk rated three | 1 | 1 |