Consolidated Statements of Comprehensive Income Consolidated Statement of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Securities, Available-for-sale, Tax	$ (55)	$ 24	$ (223)	$ 57
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	(6)	(1)	(55)	(7)
Other Comprehensive Income (Loss), Brokered Time Deposits, Tax	0	0	0	0
Other Comprehensive Income (Loss), Long Term Debt, Adjustment, Tax	0	1	1	1
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax	$ 1	$ 2	$ 1	$ 3