Balance Sheet Offsetting - Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Total
Gross Amounts of Recognized Liabilities	$ 1,043,212	$ 1,627,854
Gross Amounts Offset in the Balance Sheet	(5,836)
Net Amounts of Liabilities Presented in the Balance Sheet	1,037,376	1,627,854
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(994,459)	(1,569,729)
Net Amount	42,917	58,125
Institutional Counterparties
Securities loaned:
Gross Amounts of Recognized Liabilities	851,192	1,432,196
Net Amounts of Liabilities Presented in the Balance Sheets	851,192	1,432,196
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(797,948)	(1,359,850)
Net Amount	53,244	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	180,569	191,483
Net Amounts of Liabilities Presented in the Balance Sheet	180,569	191,483
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(193,282)	(205,734)
Net Amount	(12,713)	(14,251)
Institutional Counterparties | Forward MBS Derivatives
Derivatives:
Gross Amounts of Recognized Liabilities	11,451	2,211
Gross Amounts Offset in the Balance Sheet	(5,836)
Net Amounts of Liabilities Presented in the Balance Sheet	5,615	2,211
Gross Amounts Not Offset in the Balance Sheet
Financial Instruments	(3,229)	(2,211)
Net Amount	$ 2,386
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