Fair Value of Financial Instruments - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Assets at Fair Value:
Derivatives	$ 1,360,207	$ 611,544
Liabilities at Fair Value:
Derivatives	24,402	19,303
Agency Securities
Assets at Fair Value:
Debt securities, available-for-sale	19,991,917	19,417,640
U.S. Treasury Securities
Assets at Fair Value:
Debt securities, available-for-sale	473,975	598,109
Level 1
Assets at Fair Value:
Derivatives	227,881	17,820
Liabilities at Fair Value:
Derivatives	0	93
Level 1 \| Agency Securities
Assets at Fair Value:
Debt securities, available-for-sale	0	0
Level 1 \| U.S. Treasury Securities
Assets at Fair Value:
Debt securities, available-for-sale	473,975	598,109
Level 2
Assets at Fair Value:
Derivatives	1,132,326	593,724
Liabilities at Fair Value:
Derivatives	24,402	19,210
Level 2 \| Agency Securities
Assets at Fair Value:
Debt securities, available-for-sale	19,991,917	19,417,640
Level 2 \| U.S. Treasury Securities
Assets at Fair Value:
Debt securities, available-for-sale	0	0
Level 3
Assets at Fair Value:
Derivatives	0	0
Liabilities at Fair Value:
Derivatives	0	0
Level 3 \| Agency Securities
Assets at Fair Value:
Debt securities, available-for-sale	0	0
Level 3 \| U.S. Treasury Securities
Assets at Fair Value:
Debt securities, available-for-sale	$ 0	$ 0