Consolidated Statements of Comprehensive Income Consolidated Statement of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax	$ (38)	$ 33	$ (168)	$ 34
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	(10)	18	(49)	(6)
Other Comprehensive Income (Loss), Brokered Time Deposits, Tax	0	0	0	0
Other Comprehensive Income (Loss), Long Term Debt, Adjustment, Tax	0	1	1	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax	$ 0	$ 2	$ 1	$ 1