- Change in Each Component of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Change in accumulated other comprehensive loss balances:
Unrealized net gains (losses) on hedges arising during the period, net of tax	$ 10	$ (58)
Reclassification adjustment for net (gains) losses on hedges included in interest income for loans and interest expense on long-term debt, net of tax	14	0
Net change, before tax	33	(79)
Net change, tax	(9)	21
Net change, net of tax	24	(58)
Unrealized holding gains (losses) arising during the period on securities available for sale, net of tax	148	(193)
Reclassification adjustment for net (gains) losses on securities available for sale included in securities gains, net, net of tax	(1)	0
Other Comprehensive Income (Loss), Accretion of Fair Value Adjustment from Sale of Securities, Before Tax		0
Other Comprehensive Income (Loss), Accretion of Fair Value Adjustment from Sale of Securities,Tax		0
Other Comprehensive Income (Loss), Accretion of Fair Value Adjustment from Sale of Securities, Net of Tax		0
Amortization of net unrealized (gains) losses on held to maturity securities, net of tax	5	3
Net change, before tax	206	(258)
Net change, tax	(54)	68
Net change, net of tax	152	(190)
Foreign currency translation adjustment, net of tax	0	(2)
Amortization of prior service credit, net of tax	(7)	(8)
Recognized net actuarial (gain) loss, net of tax	13	18
Net change, before tax	8	14
Net change, tax	(2)	(4)
Net change, net of tax	6	10
Other, before tax	2	(1)
Other, tax	(1)	0
Other, net of tax	1	(1)
Other Comprehensive Income (Loss), before Tax	249	(327)
Other Comprehensive Income (Loss), Tax	(66)	86
Other Comprehensive Income (Loss), Net of Tax	183	(241)
Net Unrealized Gains (Losses) on Cash Flow Hedges
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax	14	(79)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	19	0
Reclassification from AOCI, Current Period, Tax	(5)	0
Other Comprehensive Income (Loss) before Reclassifications, Tax	(4)	21
Accumulated Net Investment Gain (Loss) Arising During the Period, Attributable to Parent [Member]
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax	200	(262)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(1)	0
Reclassification from AOCI, Current Period, Tax	0	0
Other Comprehensive Income (Loss) before Reclassifications, Tax	(52)	69
Accumulated Net Investment Gain (Loss), Held to Maturity Securities, Attributable to Parent [Member]
Change in accumulated other comprehensive loss balances:
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	7	4
Reclassification from AOCI, Current Period, Tax	(2)	(1)
Foreign Currency Translation Adjustment
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Tax	0	(3)
Other Comprehensive Income (Loss), Tax	0	1
Other Comprehensive Income (Loss), Net of Tax	0
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(10)	(10)
Other Comprehensive Income (Loss) before Reclassifications, Tax	3	2
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax	18	24
Other Comprehensive Income (Loss) before Reclassifications, Tax	$ (5)	$ (6)