Derivative Financial Instruments and Off-balance sheet Financial Instruments - Summary of the volume and fair value positions (Details) $ in Millions	Dec. 31, 2021 USD ($) contract	Dec. 31, 2020 USD ($) contract
Derivatives, Fair Value
Total asset derivatives, notional amount	$ 1,285	$ 2,009
Total liability derivatives, notional amount	790	3,182
Total derivatives, notional amount	$ 2,075	$ 5,191
Total asset derivatives, number of contracts | contract	1,355	4,440
Total liability derivatives, number of contracts | contract	37,928	4,108
Total derivatives, number of contracts | contract	39,283	8,548
Net amount on balance sheet	$ 76	$ 206
Net amount on balance sheet	9	(655)
Total derivatives, fair value, net	85	(449)
Asset derivatives, gross asset	77	218
Liability derivatives, gross asset	23	2
Asset derivatives, gross liability	(1)	(12)
Liability derivatives, gross liability	$ (14)	(657)
Liabilities held for sale
Derivatives, Fair Value
Total liability derivatives, notional amount		$ 2,240
Total liability derivatives, number of contracts | contract		2,737
Net amount on balance sheet		$ (630)
Liability derivatives, gross asset		1
Liability derivatives, gross liability		(631)
Assets held for sale
Derivatives, Fair Value
Total asset derivatives, notional amount		$ 158
Total asset derivatives, number of contracts | contract		3,189
Net amount on balance sheet		$ 185
Asset derivatives, gross asset		189
Asset derivatives, gross liability		$ (4)
Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, number of contracts | contract		705
Net amount on balance sheet		$ 0
Liability derivatives, gross asset		0
Liability derivatives, gross liability		$ 0
Futures | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, number of contracts | contract	1,181	290
Net amount on balance sheet	$ 1	$ 0
Asset derivatives, gross asset	1	0
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	36,668
Net amount on balance sheet	$ (2)
Liability derivatives, gross asset	0
Liability derivatives, gross liability	$ (2)
Options | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, number of contracts | contract	61	56
Net amount on balance sheet	$ 5	$ 6
Asset derivatives, gross asset	5	6
Asset derivatives, gross liability	$ 0	$ 0
Futures | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, number of contracts | contract	113	905
Net amount on balance sheet	$ 0	$ 1
Asset derivatives, gross asset	0	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	1,260	666
Net amount on balance sheet	$ (1)	$ 0
Liability derivatives, gross asset	0	0
Liability derivatives, gross liability	(1)	0
Total return swap agreements - fixed income | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount		50
Net amount on balance sheet		0
Liability derivatives, gross asset		0
Liability derivatives, gross liability		0
Foreign currency forwards | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	2	291
Net amount on balance sheet	0	4
Asset derivatives, gross asset	0	9
Asset derivatives, gross liability	0	(5)
Foreign currency forwards | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount	715	250
Net amount on balance sheet	16	(9)
Liability derivatives, gross asset	23	1
Liability derivatives, gross liability	(7)	(10)
Embedded derivative financial instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, notional amount	750	750
Net amount on balance sheet	0	0
Asset derivatives, gross asset	0	0
Asset derivatives, gross liability	0	0
Contingent consideration | Other assets
Derivatives, Fair Value
Total asset derivatives, notional amount	250
Net amount on balance sheet	65
Asset derivatives, gross asset	65
Asset derivatives, gross liability	0
Credit default swaps – buying protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	33	60
Net amount on balance sheet	(1)	(3)
Asset derivatives, gross asset	0	0
Asset derivatives, gross liability	(1)	(3)
Credit default swaps – buying protection | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount	70	638
Net amount on balance sheet	(4)	(16)
Liability derivatives, gross asset	0	0
Liability derivatives, gross liability	(4)	(16)
Credit default swaps – selling protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	250	750
Net amount on balance sheet	6	13
Asset derivatives, gross asset	6	13
Asset derivatives, gross liability	0	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	5	4
Net amount on balance sheet	0	0
Liability derivatives, gross asset	0	0
Liability derivatives, gross liability	$ 0	$ 0