Derivative Instruments - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Derivative [Line Items]
Cash collateral payable to trade counterparties	$ 9,200		$ 9,200		$ 2,900
Cash collateral received	3,000		3,000		5,600
Gains (losses) on equity options activity	(7,800)	$ (1,700)	(9,800)	$ 3,100
Exchange-traded options | Long
Derivative [Line Items]
Cash collateral payable to trade counterparties	0		0		0
Long exchange-traded equity options	100		100		1,900
Exchange-traded options | Short
Derivative [Line Items]
Cash collateral received	0		0		0
Short exchange-traded equity options, included in securities sold not yet purchased	$ 0		$ 0		$ 2,800