Derivative Instruments - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Derivative [Line Items]
Cash collateral payable to trade counterparties	$ 16,000,000		$ 16,000,000		$ 2,900,000
Cash collateral received	0		0		5,600,000
Gains (losses) on equity options activity	3,600,000	$ (500,000)	13,400,000	$ 2,600,000
Exchange-traded options | Long
Derivative [Line Items]
Cash collateral payable to trade counterparties	0		0		0
Long exchange-traded equity options	4,800,000		4,800,000		1,900,000
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	$ 200,000		$ 200,000		$ 2,800,000