Consolidated Statements of Comprehensive Income Consolidated Statement of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax	$ 29	$ (117)	$ (93)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	0	(145)	(5)
Other Comprehensive Income (Loss), Brokered Time Deposits, Tax	0	0	0
Other Comprehensive Income (Loss), Long Term Debt, Adjustment, Tax	3	(1)	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax	$ 138	$ 52	$ (103)