Balance Sheet Offsetting - Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Reverse repurchase agreements:
Net Amounts of Assets Presented in the Balance Sheet	$ 81,766	$ 80,011
Total
Gross Amounts of Recognized Assets	1,213,073	1,553,386
Net Amounts of Assets Presented in the Balance Sheet	1,213,073	1,553,386
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(1,105,971)	(1,413,061)
Cash Collateral Pledged	(34,195)	(49,253)
Net Amount	72,907	91,072
Institutional Counterparties
Securities borrowed:
Gross Amounts of Recognized Assets	1,077,956	1,406,937
Net Amounts of Assets Presented in the Balance Sheet	1,077,956	1,406,937
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(1,023,786)	(1,332,856)
Net Amount	54,170	74,081
Interest Rate Swap | Institutional Counterparties
Derivatives:
Gross Amounts of Recognized Assets	34,195	49,253
Net Amounts of Assets Presented in the Balance Sheet	34,195	49,253
Gross Amounts Not Offset in the Balance Sheet
Cash Collateral Pledged	(34,195)	(49,253)
Net Amount	0
Reverse repurchase agreements | Institutional Counterparties
Reverse repurchase agreements:
Gross Amounts of Recognized Assets	81,766	80,011
Net Amounts of Assets Presented in the Balance Sheet	81,766	80,011
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(81,340)	(80,011)
Net Amount	426	0
Forward MBS Derivatives | Institutional Counterparties
Derivatives:
Gross Amounts of Recognized Assets	19,156	16,755
Net Amounts of Assets Presented in the Balance Sheet	19,156	16,755
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(845)	(194)
Net Amount	$ 18,311	16,561
Treasury Futures And Option Derivatives | Institutional Counterparties
Derivatives:
Gross Amounts of Recognized Assets		430
Net Amounts of Assets Presented in the Balance Sheet		430
Gross Amounts Not Offset in the Balance Sheet
Net Amount		$ 430