Offsetting Assets and Liabilities - Offsetting Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivative Liability [Abstract]
Cash Collateral Pledged	$ (3,600)	$ (4,300)
Securities loaned
Securities Borrowed [Abstract]
Gross Amounts of Recognized Liabilities	15,150
Gross Amounts Offset in the Statement of Financial Condition	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	15,150
Financial Instruments	0
Cash Collateral Pledged	(14,254)
Net Amount	896
Derivatives
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	28,230	19,259
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	28,230	19,259
Financial Instruments	0	0
Cash Collateral Pledged	(3,553)	(4,276)
Net Amount	24,677	14,983
Exchange-traded options \| Short
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	11,091	12,348
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	11,091	12,348
Financial Instruments	0	0
Cash Collateral Pledged	0	0
Net Amount	$ 11,091	$ 12,348

Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

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