Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	$ 7,969	$ 11,342
Net Amount of Liabilities Presented in the Balance Sheet	2,471	1,009
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
MBS	3,181,839	2,596,255
Mortgage loans held for investment, at fair value	4,268	6,264
Total assets carried at fair value	3,194,076	2,613,861
Total liabilities carried at fair value	2,471	1,009
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
MBS	0	0
Mortgage loans held for investment, at fair value	0	0
Total assets carried at fair value	0	1,094
Total liabilities carried at fair value	2,471	902
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
MBS	3,181,041	2,594,980
Mortgage loans held for investment, at fair value	0	0
Total assets carried at fair value	3,189,010	2,605,228
Total liabilities carried at fair value	0	107
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
MBS	798	1,275
Mortgage loans held for investment, at fair value	4,268	6,264
Total assets carried at fair value	5,066	7,539
Total liabilities carried at fair value	0	0
Fair Value, Measurements, Recurring | Options on U.S. Treasury futures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	0	1,094
Fair Value, Measurements, Recurring | Options on U.S. Treasury futures | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	0	1,094
Fair Value, Measurements, Recurring | Options on U.S. Treasury futures | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	0	0
Fair Value, Measurements, Recurring | Options on U.S. Treasury futures | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	0	0
Fair Value, Measurements, Recurring | Interest rate swaptions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	3,202	1,360
Net Amount of Liabilities Presented in the Balance Sheet	0	107
Fair Value, Measurements, Recurring | Interest rate swaptions | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	0	0
Net Amount of Liabilities Presented in the Balance Sheet	0	0
Fair Value, Measurements, Recurring | Interest rate swaptions | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	3,202	1,360
Net Amount of Liabilities Presented in the Balance Sheet	0	107
Fair Value, Measurements, Recurring | Interest rate swaptions | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	0	0
Net Amount of Liabilities Presented in the Balance Sheet	0	0
Fair Value, Measurements, Recurring | U.S. Treasury futures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Liabilities Presented in the Balance Sheet	2,471	902
Fair Value, Measurements, Recurring | U.S. Treasury futures | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Liabilities Presented in the Balance Sheet	2,471	902
Fair Value, Measurements, Recurring | U.S. Treasury futures | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Liabilities Presented in the Balance Sheet	0	0
Fair Value, Measurements, Recurring | U.S. Treasury futures | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Liabilities Presented in the Balance Sheet	0	0
Fair Value, Measurements, Recurring | TBA securities | Long position
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	4,767	8,888
Fair Value, Measurements, Recurring | TBA securities | Level 1 | Long position
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	0	0
Fair Value, Measurements, Recurring | TBA securities | Level 2 | Long position
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	4,767	8,888
Fair Value, Measurements, Recurring | TBA securities | Level 3 | Long position
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Amount of Assets Presented in the Balance Sheet	$ 0	$ 0