Fair Value of Financial Instruments Table of Significant Observable Inputs used in the Valuation of Nonperforming Loans (Details) - Non-performing loans - Investment in Loans - Significant unobservable inputs Level 3 - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate		30.00%	30.00%
Loan resolution time-line (Years)		2 years	2 years 3 months 17 days
Value of underlying properties		$ 1,775	$ 1,775
Holding costs		21.10%	22.00%
Liquidation costs		15.90%	16.80%
Fair Value Inputs, Note Rate		6.00%	6.00%
Secondary market transaction prices/UPB		88.50%	88.50%
Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate		16.00%	16.00%
Loan resolution time-line (Years)		4 months 24 days	5 months 30 days
Value of underlying properties		$ 45	$ 40
Holding costs		4.80%	5.30%
Liquidation costs		8.40%	8.40%
Fair Value Inputs, Note Rate		3.00%	3.00%
Secondary market transaction prices/UPB		75.50%	75.50%
Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	[1]	23.80%	23.50%
Loan resolution time-line (Years)	[1]	1 year 3 months 19 days	1 year 2 months 12 days
Value of underlying properties	[1]	$ 335	$ 306
Holding costs	[1]	7.20%	7.60%
Liquidation costs	[1]	9.30%	9.40%
Fair Value Inputs, Note Rate	[1]	4.90%	4.80%
Secondary market transaction prices/UPB	[1]	83.80%	83.40%

[1] Weighted based on value of underlying properties (excluding the value of underlying properties line item).