Derivative Financial Instruments - Summary of the volume and fair value positions of derivative instruments (Details) $ in Millions	Jun. 30, 2022 USD ($) contract	Dec. 31, 2021 USD ($) contract
Derivatives, Fair Value
Total asset derivatives, notional amount	$ 2,619	$ 1,285
Total liability derivatives, notional amount	1,155	790
Total derivatives, notional amount	$ 3,774	$ 2,075
Total asset derivatives, number of contracts | contract	4,818	1,355
Total liability derivatives, number of contracts | contract	47,460	37,928
Total derivatives, Number of contracts | contract	52,278	39,283
Net amount on balance sheet	$ 162	$ 76
Net amount on balance sheet	(11)	9
Total derivatives, fair value, net	151	85
Gross amount	165	77
Liability derivatives, gross asset	52	23
Asset derivatives, gross liability	(3)	(1)
Liability derivatives gross amount	$ (63)	$ (14)
Futures | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, number of contracts | contract	3,484	1,181
Net amount on balance sheet	$ 3	$ 1
Gross amount	3	1
Asset derivatives, gross liability	$ 0	$ 0
Futures | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, number of contracts | contract	45,044	36,668
Net amount on balance sheet	$ (38)	$ (2)
Liability derivatives, gross asset	0	0
Liability derivatives gross amount	$ (38)	$ (2)
Options | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, number of contracts | contract	1,334	61
Net amount on balance sheet	$ 39	$ 5
Gross amount	39	5
Asset derivatives, gross liability	$ 0	$ 0
Options | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, number of contracts | contract	1,212
Net amount on balance sheet	$ (19)
Liability derivatives, gross asset	0
Liability derivatives gross amount	$ (19)
Futures | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, number of contracts | contract		113
Net amount on balance sheet		$ 0
Gross amount		0
Asset derivatives, gross liability		$ 0
Futures | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, number of contracts | contract	1,204	1,260
Net amount on balance sheet	$ (1)	$ (1)
Liability derivatives, gross asset	0	0
Liability derivatives gross amount	(1)	(1)
Foreign currency forwards | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	111	2
Net amount on balance sheet	(1)	0
Gross amount	1	0
Asset derivatives, gross liability	(2)	0
Foreign currency forwards | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount	666	715
Net amount on balance sheet	47	16
Liability derivatives, gross asset	52	23
Liability derivatives gross amount	(5)	(7)
Embedded derivative financial instruments | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	750	750
Net amount on balance sheet	0	0
Gross amount	0	0
Asset derivatives, gross liability	0	0
Contingent consideration | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	250	250
Net amount on balance sheet	108	65
Gross amount	108	65
Asset derivatives, gross liability	0	0
Credit default swaps – buying protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	1,508	33
Net amount on balance sheet	13	(1)
Gross amount	14	0
Asset derivatives, gross liability	(1)	(1)
Credit default swaps – buying protection | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount	39	70
Net amount on balance sheet	0	(4)
Liability derivatives, gross asset	0	0
Liability derivatives gross amount	0	(4)
Credit default swaps – selling protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount		250
Net amount on balance sheet		6
Gross amount		6
Asset derivatives, gross liability		0
Credit default swaps – selling protection | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount	450	5
Net amount on balance sheet	0	0
Liability derivatives, gross asset	0	0
Liability derivatives gross amount	$ 0	$ 0