Derivative Instruments and Hedging Activities (Statement of Gains and Losses on Derivative Instruments Reported in Statement of Comprehensive Income) (Details) - Not designated as hedging instrument - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments, net, pretax	$ (14)	$ 13	$ (9)
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments, net, pretax	(10)	0	(2)
Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments, net, pretax	(4)	13	(7)
Gains on mortgage and automotive loans | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments, net, pretax	1	0	1
Other income, net of losses | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments, net, pretax	(11)	0	(3)
Other income, net of losses | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments, net, pretax	0	13	(7)
Other operating expenses | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments, net, pretax	$ (4)	$ 0	$ 0