Balance Sheet Offsetting - Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Reverse repurchase agreements:
Net Amounts of Assets Presented in the Balance Sheet	$ 145,365	$ 118,262
Total
Gross Amounts of Recognized Assets	1,403,484	1,639,589
Gross Amounts Offset in the Balance Sheet	(686)	(1,773)
Net Amounts of Assets Presented in the Balance Sheet	1,402,798	1,637,816
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(1,308,549)	(1,564,596)
Net Amount	94,249	73,220
Institutional Counterparties
Securities borrowed:
Gross Amounts of Recognized Assets	1,182,934	1,518,372
Net Amounts of Assets Presented in the Balance Sheet	1,182,934	1,518,372
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(1,126,566)	(1,445,590)
Net Amount	56,368	72,782
Interest rate swaps | Institutional Counterparties
Derivatives:
Gross Amounts of Recognized Assets	2,976
Net Amounts of Assets Presented in the Balance Sheet	2,976
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(2,953)
Net Amounts of Assets Presented in the Balance Sheet	23
Credit default swaps | Institutional Counterparties
Derivatives:
Gross Amounts of Recognized Assets	5
Net Amounts of Assets Presented in the Balance Sheet	5
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(5)
Net Amounts of Assets Presented in the Balance Sheet	0
Reverse repurchase agreements | Institutional Counterparties
Reverse repurchase agreements:
Gross Amounts of Recognized Assets	145,365	118,262
Net Amounts of Assets Presented in the Balance Sheet	145,365	118,262
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(139,187)	(118,262)
Net Amount	6,178	0
Forward MBS Derivatives | Institutional Counterparties
Derivatives:
Gross Amounts of Recognized Assets	72,204	2,955
Gross Amounts Offset in the Balance Sheet	(686)	(1,773)
Net Amounts of Assets Presented in the Balance Sheet	71,518	1,182
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(39,838)	(744)
Net Amounts of Assets Presented in the Balance Sheet	$ 31,680	$ 438