Fair Value of Financial Instruments Recorded basis and Fair Value (Details) - USD ($) $ in Thousands		Sep. 30, 2018		Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage-backed securities		$ 3,294,510		$ 3,026,989
U.S. Treasuries		0		146,530
Derivative assets		2,612		2,940
Derivative liabilities		2,039		269
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage-backed securities		3,294,510		3,026,989
U.S. Treasuries		0		146,530
Mortgage loans held for investment, net (1)		12,342		15,738
Derivative assets		2,612		2,940
Repurchase agreements (2)		2,690,858		2,565,902
Non-recourse collateralized financing (1)		3,709		5,520
Derivative liabilities		2,039		269
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage-backed securities		3,294,510		3,026,989
U.S. Treasuries		0		146,530
Mortgage loans held for investment, net (1)	[1]	9,165		12,973
Derivative assets		2,612		2,940
Repurchase agreements (2)		2,690,858	[2]	2,565,902
Non-recourse collateralized financing (1)	[1]	3,742		5,554
Derivative liabilities		$ 2,039		$ 269

[1] The Company determines the fair value of its mortgage loans held for investment, net and its non-recourse collateralized financing using internally developed cash flow models with inputs similar to those used to estimate the fair value of the Company’s Level 3 non-Agency MBS.

[2] The carrying value of repurchase agreements generally approximates fair value due to their short-term maturities.