Consolidated Statements of Comprehensive Income Consolidated Statement of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax	$ 24	$ (19)	$ 57	$ 228
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	(1)	(51)	(7)	81
Other Comprehensive Income (Loss), Long Term Debt, Adjustment, Tax	1	(2)	1	(3)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax	$ 2	$ 2	$ 3	$ 39