Hedging transactions and derivative financial instruments Hedging transactions and derivative financial instruments (Summary of Notional Values and Pretax Impact in Fair Values) (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Derivative and nonderivative, original notional amount	$ 13,001	$ 11,448
Derivative and nonderivative, notional amount	11,276	10,573
Gain (loss) recognized in OCI on derivatives and nonderivatives	5	(954)
Net investment hedging | Foreign currency contracts
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, original notional amount	1,875	2,875
Derivative, notional amount outstanding	1,000	2,000
Gain (loss) recognized in OCI on derivatives	24	(104)
Net investment hedging | Foreign currency denominated debt
Derivative Instruments, Gain (Loss) [Line Items]
Nonderivative hedging instruments	6,276	4,573
Gain (loss) recognized in OCI on nonderivatives	130	(418)
Cash flow hedging | Foreign currency contracts
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, original notional amount	4,000	4,000
Derivative, notional amount outstanding	4,000	4,000
Gain (loss) recognized in OCI on derivatives	(112)	$ (432)
Cash flow hedging | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, original notional amount	850
Derivative, notional amount outstanding	0
Gain (loss) recognized in OCI on derivatives	$ (37)