Accumulated Other Comprehensive (Loss) Income (Before and After Tax) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Tax [Abstract]
Other compehrensive income (loss), investment securities, net unrealized gains (losses) arising during the period, before tax	$ 404	$ (95)	$ 825	$ (531)
Other compehrensive income (loss), investement securities, net realized gains reclassified to income from continuing operations, before tax	24	1	33	7
Other comprehensive income, investment securities, net change, before tax	380	(96)	792	(538)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Tax [Abstract]
Other comprehensive income (loss), investment securities, unrealized holding gains (losses) arising during the period, tax	(95)	22	(194)	125
Other comprehensive income (loss), investment securities, net realized gains reclassified to income from continuing operations, tax effect	(6)	0	(8)	(1)
Other comprehensive income (loss), investment securities, net change, tax effect	(89)	22	(186)	126
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax [Abstract]
Other comprehensive income (loss), investment securities, net unrealized gains (losses) arising during the period, after tax	309	(73)	631	(406)
Other comprehensive income (loss), investment securities, net realized gains reclassified to income from continuing operations, after tax	18	1	25	6
Other comprehensive income (loss), investment securities, net change, after tax	291	(74)	606	(412)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax [Abstract]
Other comprehensive income (loss), translation adjustments, net change, before tax	4	(3)	6	(8)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax [Abstract]
Other comprehensive income (loss), translation adjustments, net unrealized gains (losses) arising during the period, tax effect	(1)	1	(2)	2
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, after tax	3	(2)	4	(6)
Other Comprehensive Income (Loss), Net investment hedges, before Tax [Abstract]
Other comprehensive income (loss), net investment hedges, unrealized gains (losses) arising during the period, before tax	(3)	3	(5)	7
Other Comprehensive Income (Loss), Net investment hedges, Tax [Abstract]
Other comprehensive income (loss), net investment hedges, net unrealized gains arising during the period, tax effect	1	(1)	2	(2)
Other Comprehensive Income (Loss), Net investment hedges, Net of Tax [Abstract]
Net investment hedges, unrealized gains (losses) arising during the period, after tax	(2)	2	(3)	5
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax [Abstract]
Other comprehensive income (loss), cash flow hedges, net unrealized gains (losses) arising during the period before tax	26	5	21	23
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, before tax	4		9
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification, before tax	22		12
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax [Abstract]
Other comprehensive income (loss), cash flow hedges, net unrealized gains arising during the period, tax	(6)	(2)	(5)	(6)
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, tax	(1)		(2)
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification, tax	(5)		(3)
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	20	3	16	17
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, after tax	3		7
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification and tax	17		9
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Tax [Abstract]
Other comprehensive income (loss), defined benefit pension plans, net unrealized gains (losses) arising during period, before tax		1	(1)	(2)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Tax [Abstract]
Other comprehensive income (loss), defined benefit pension plans, net unrealized gains (losses) arising during period, tax		0	0	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Net of Tax [Abstract]
Other comprehensive (income), defined benefit pension plans, net unrealized gains (losses) arising during period, after tax	0	1	(1)	(2)
Other Comprehensive Income (Loss), before Tax [Abstract]
Other comprehensive income (loss), before tax	403	(90)	804	(518)
Other Comprehensive Income (Loss), Tax [Abstract]
Other comprehensive income (loss), tax effect	(94)	20	(189)	120
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other comprehensive income (loss), net of tax	$ 309	$ (70)	$ 615	$ (398)