Derivatives - TBA Agency Securities (Details) - USD ($)	Jun. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Notional Amount	$ 6,910,000,000	$ 7,210,000,000
Notional amount, forward settling	$ 550,000,000
TBA Agency Securities, 15-year, 1.5%
Derivative [Line Items]
Fixed interest rate		1.50%
Notional Amount		$ 1,000,000,000
Cost Basis		999,840,000
Fair Value		$ 1,003,125,000
TBA Agency Securities, 15-year, 2.0%
Derivative [Line Items]
Fixed interest rate		2.00%
Notional Amount		$ 1,700,000,000
Cost Basis		1,733,652,000
Fair Value		$ 1,738,695,000
TBA Agency Securities, 30-year, 4.5%
Derivative [Line Items]
Fixed interest rate	4.50%
Notional Amount	$ 375,000,000
Cost Basis	377,955,000
Fair Value	$ 376,919,000
TBA Agency Securities, 30-year, 5.0%
Derivative [Line Items]
Fixed interest rate	5.00%
Notional Amount	$ 300,000,000
Cost Basis	304,742,000
Fair Value	306,433,000
TBA Agency Securities, 30-year, 2.0%
Derivative [Line Items]
Fixed interest rate		2.00%
Notional Amount		$ 300,000,000
Cost Basis		300,789,000
Fair Value		$ 299,227,000
TBA Agency Securities, 30-year, 2.5%
Derivative [Line Items]
Fixed interest rate		2.50%
Notional Amount		$ 1,200,000,000
Cost Basis		1,224,820,000
Fair Value		$ 1,223,510,000
TBA Agency Securities, 30-year, 3.0%
Derivative [Line Items]
Fixed interest rate		3.00%
Notional Amount		$ 300,000,000
Cost Basis		309,734,000
Fair Value		310,503,000
TBA Agency Securities
Derivative [Line Items]
Notional Amount	675,000,000	4,500,000,000
Cost Basis	682,697,000	4,568,835,000
Fair Value	683,352,000	4,575,060,000
Notional amount, forward settling	$ 1,225,000,000	$ 400,000,000