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, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments, net, pretax	$ 13	$ (9)	$ (1)
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on interest rate derivative instruments	0	(2)	0
Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on foreign currency derivative instruments	13	(7)	(1)
Gains on mortgage and automotive loans | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on interest rate derivative instruments	0	1	0
Other income | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on interest rate derivative instruments	0	(3)	0
Other income | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on foreign currency derivative instruments	13	(7)	1
Interest expense | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on foreign currency derivative instruments	$ 0	$ 0	$ (2)