Accumulated Other Comprehensive (Loss) Income (Before and After Tax) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
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	$ 702	$ 421
Other compehrensive income (loss), investement securities, net realized gains reclassified to income from continuing operations, before tax	105	9
Other comprehensive income, investment securities, net change, before tax	597	412
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	(168)	(99)
Other comprehensive income (loss), investment securities, net realized gains reclassified to income from continuing operations, tax effect	(24)	(2)
Other comprehensive income (loss), investment securities, net change, tax effect	(144)	(97)
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	534	322
Other comprehensive income (loss), investment securities, net realized gains reclassified to income from continuing operations, after tax	81	7
Other comprehensive income (loss), investment securities, net change, after tax	453	315
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax [Abstract]
Other comprehensive income (loss), translation adjustments, net change, before tax	(13)	2
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	3	(1)
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	(10)	1
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	12	(2)
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	(3)	1
Other Comprehensive Income (Loss), Net investment hedges, Net of Tax [Abstract]
Net investment hedges, unrealized gains (losses) arising during the period, after tax	9	(1)
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	169	(5)
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, before tax		5
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification, before tax		(10)
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	(41)	1
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, tax		(1)
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification, tax		2
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	128	(4)
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, after tax		4
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification and tax		(8)
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	4	(1)
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	(1)	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	3	(1)
Other Comprehensive Income (Loss), before Tax [Abstract]
Other comprehensive income (loss), before tax	769	401
Other Comprehensive Income (Loss), Tax [Abstract]
Other comprehensive income (loss), tax effect	(186)	(95)
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other comprehensive income (loss), net of tax	$ 583	$ 306