Investments in Securities - Schedule of Available-for-sale Securities in an Unrealized Gain or Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Debt and Equity Securities, FV-NI [Line Items]
Principal Amount	$ 15,412,104
Amortized Cost	15,244,891
Gross Unrealized Loss	(203,150)
Gross Unrealized Gain	76,354
Fair Value	15,118,095
Agency Securities
Debt and Equity Securities, FV-NI [Line Items]
Principal Amount	14,812,104	$ 12,957,039
Amortized Cost	14,642,824	12,806,504
Gross Unrealized Loss	(203,150)	(370,044)
Gross Unrealized Gain	76,171	2,954
Fair Value	14,515,845	$ 12,439,414
U.S. Treasury Securities
Debt and Equity Securities, FV-NI [Line Items]
Principal Amount	600,000
Amortized Cost	602,067
Gross Unrealized Loss	0
Gross Unrealized Gain	183
Fair Value	$ 602,250

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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+ Details