Valuation Qualtitative Information (Details) - Level 3 [Member] - USD ($)		Sep. 30, 2018	Dec. 31, 2017
Non-Agency RMBS [Member] | Market Quotes [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		$ 6,387,000	$ 2,258,000
Non-Agency RMBS [Member] | Market Quotes [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Binding Third-Party Valuation		53.49	57.84
Non-Agency RMBS [Member] | Market Quotes [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Binding Third-Party Valuation		90.37	87.45
Non-Agency RMBS [Member] | Market Quotes [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Binding Third-Party Valuation	[1]	76.94	78.02
Non-Agency RMBS [Member] | Discounted Cash Flows [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		$ 1,246,000	$ 6,574,000
Non-Agency RMBS [Member] | Discounted Cash Flows [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield		3.70%	4.60%
Projected Collateral Prepayments		51.70%	19.20%
Projected Collateral Losses		4.40%	0.90%
Projected Collateral Recoveries		10.30%	8.80%
Projected Collateral Scheduled Amortization		18.00%	33.10%
Non-Agency RMBS [Member] | Discounted Cash Flows [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield		4.90%	5.10%
Projected Collateral Prepayments		66.50%	44.90%
Projected Collateral Losses		9.30%	20.10%
Projected Collateral Recoveries		11.90%	31.50%
Projected Collateral Scheduled Amortization		28.00%	47.50%
Non-Agency RMBS [Member] | Discounted Cash Flows [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield	[1]	4.10%	4.80%
Projected Collateral Prepayments	[1]	60.40%	26.50%
Projected Collateral Losses	[1]	6.40%	9.20%
Projected Collateral Recoveries	[1]	10.80%	22.50%
Projected Collateral Scheduled Amortization	[1]	22.40%	41.80%
Projected Total	[1]	100.00%	100.00%
Interest-Only [Member] | Agency RMBS [Member] | Valuation, Income Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		$ 4,108,000	$ 2,254,000
Interest-Only [Member] | Agency RMBS [Member] | Valuation, Income Approach [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Projected Collateral Prepayments		31.70%	43.80%
Projected Collateral Scheduled Amortization		30.60%	11.90%
LIBOR OAS	[2]	5.48%	6.27%
Interest-Only [Member] | Agency RMBS [Member] | Valuation, Income Approach [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Projected Collateral Prepayments		69.40%	88.10%
Projected Collateral Scheduled Amortization		68.30%	56.20%
LIBOR OAS	[2]	14.26%	14.08%
Interest-Only [Member] | Agency RMBS [Member] | Valuation, Income Approach [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Projected Collateral Prepayments	[1]	58.40%	71.20%
Projected Collateral Scheduled Amortization	[1]	41.60%	28.80%
Projected Total	[1]	100.00%	100.00%
LIBOR OAS	[1],[2]	6.34%	7.81%

[1] Averages are weighted based on the fair value of the related instrument.

[2] Shown in basis points.