Offsetting Assets and Liabilities - Offsetting Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Securities Loaned [Abstract]
Gross Amounts of Recognized Liabilities	$ 23,911
Gross Amounts Offset in the Statement of Financial Condition	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	23,911
Financial Instruments Collateral	23,373
Cash Collateral Pledged	0
Net Amount	538
Derivative Liability [Abstract]
Cash Collateral Pledged	(5,600)	$ (6,400)
Derivatives
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	16,923	30,537
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	16,923	30,537
Financial Instruments Collateral	0	0
Cash Collateral Pledged	(5,572)	(6,374)
Net Amount	11,351	24,163
Exchange-traded options | Short exchange-traded options
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	2,774	12,486
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	2,774	12,486
Financial Instruments Collateral	0	0
Cash Collateral Pledged	0	0
Net Amount	$ 2,774	$ 12,486