Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income	$ 1,263	$ 929	$ 1,067
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent [Abstract]
Other comprehensive income (loss), investment securities, net unrealized gains (losses) arising during the period	(287)	192	33
Other comprehensive income (loss), investment securities, net realized gains (losses) reclassified to net income	8	92	147
Other comprehensive income (loss), investment securities, net change, after tax	(295)	100	(114)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax [Abstract]
Other comprehensive income (loss), translation adjustments, net unrealized gains (losses) arising during the period	(11)	8	3
Other comprehensive income (loss), translation adjustments, net realized gains (losses) reclassified to net income	0	0	(1)
Other comprehensive income (loss), translation adjustments, net unrealized gains (losses) arising during the period, after tax	(11)	8	4
Other comprehensive income (loss), net investment hedges, net unrealized gains (losses) arising during the period	9	(6)	1
Other comprehensive income (loss), translation adjustments and net investment hedges, net change	(2)	2	5
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract]
Other comprehensive income (loss), cash flow hedges, net unrealized gains (losses) arising during the period	10	3	0
Other comprehensive income (loss), cash flow hedges, net realized gains (losses) reclassified to net income	2	0	0
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification and tax	8	3	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax [Abstract]
Other comprehensive (income) loss, defined benefit pension plans, net unrealized gains (losses) arising during the period	0	1	(3)
Other comprehensive income (loss), defined benefit pension plans, net realized gains (losses) reclassified to net income	0	0	(2)
Other comprehensive (income) loss, defined benefit pension plan, net change	0	1	(1)
Other comprehensive income (loss), net of tax	(289)	106	(110)
Comprehensive income	974	1,035	957
Retained earnings
Net income	$ 1,263	$ 929	$ 1,067