- Change in Each Component of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Change in accumulated other comprehensive loss balances:
Unrealized net gains (losses) on hedges arising during the period, net of tax	$ 312	$ 10
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	14
Net change, before tax	442	33
Net change, tax	(116)	(9)
Net change, net of tax	326	24
Unrealized holding gains (losses) arising during the period on securities available for sale, net of tax	292	148
Reclassification adjustment for net (gains) losses on securities available for sale included in securities gains, net, net of tax	(39)	(1)
Amortization of net unrealized (gains) losses on held to maturity securities, net of tax	5	5
Net change, before tax	350	206
Net change, tax	(92)	(54)
Net change, net of tax	258	152
Amortization of prior service credit, net of tax	(5)	(7)
Recognized net actuarial (gain) loss, net of tax	21	13
Net change, before tax	21	8
Net change, tax	(5)	(2)
Net change, net of tax	16	6
Other, before tax		2
Other, tax		(1)
Other Comprehensive Income, Other, Net of Tax		1
Other, net of tax	0	1
Other Comprehensive Income (Loss), before Tax	813	249
Other Comprehensive Income (Loss), Tax	(213)	(66)
Other Comprehensive Income (Loss), Net of Tax	600	183
Net Unrealized Gains (Losses) on Cash Flow Hedges
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax	423	14
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	19	19
Reclassification from AOCI, Current Period, Tax	(5)	(5)
Other Comprehensive Income (Loss) before Reclassifications, Tax	(111)	(4)
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	396	200
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(53)	(1)
Reclassification from AOCI, Current Period, Tax	14	0
Other Comprehensive Income (Loss) before Reclassifications, Tax	(104)	(52)
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	7
Reclassification from AOCI, Current Period, Tax	(2)	(2)
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	(7)	(10)
Other Comprehensive Income (Loss) before Reclassifications, Tax	2	3
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	28	18
Other Comprehensive Income (Loss) before Reclassifications, Tax	$ (7)	$ (5)