Balance Sheet Offsetting - Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Total
Gross Amounts of Recognized Liabilities	$ 1,402,702	$ 1,627,854
Net Amounts of Liabilities Presented in the Balance Sheet	1,402,702	1,627,854
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(1,365,676)	(1,569,729)
Net Amount	37,026	58,125
Institutional Counterparties
Securities loaned:
Gross Amounts of Recognized Liabilities	1,072,408	1,432,196
Net Amounts of Liabilities Presented in the Balance Sheets	1,072,408	1,432,196
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(1,017,959)	(1,359,850)
Net Amount	54,449	72,346
Institutional Counterparties | Interest rate swaps
Derivatives:
Gross Amounts of Recognized Liabilities		1,949
Net Amounts of Liabilities Presented in the Balance Sheet		1,949
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments		(1,919)
Net Amount		30
Institutional Counterparties | Repurchase agreements
Repurchase agreements:
Gross Amounts of Recognized Liabilities	302,030	191,483
Net Amounts of Liabilities Presented in the Balance Sheet	302,030	191,483
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(319,453)	(205,734)
Net Amount	(17,423)	(14,251)
Institutional Counterparties | Forward MBS Derivatives
Derivatives:
Gross Amounts of Recognized Liabilities	28,264	2,211
Net Amounts of Liabilities Presented in the Balance Sheet	28,264	2,211
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(28,264)	(2,211)
Net Amount	$ 0
Institutional Counterparties | Credit default swaps
Derivatives:
Gross Amounts of Recognized Liabilities		15
Net Amounts of Liabilities Presented in the Balance Sheet		15
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments		(15)
Net Amount		$ 0