- Change in Each Component of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019		Sep. 30, 2020	Sep. 30, 2019
Change in accumulated other comprehensive loss balances:
Unrealized net gains (losses) on hedges arising during the period, before tax		$ 41
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax		11
Unrealized net gains (losses) on hedges arising during the period, net of tax		30		$ 352	$ 81
Reclassification adjustment for net (gains) losses on hedges included in interest income for loans and interest expense on long-term debt, net of tax	$ (15)	20		(7)	49
Net change, before tax	(20)	68		468	177
Net change, tax	5	(18)		(123)	(47)
Net change, net of tax	(15)	50		345	130
Unrealized holding gains (losses) arising during the period on securities available for sale, net of tax	58	53		564	358
Reclassification adjustment for net (gains) losses on securities available for sale included in securities gains, net, net of tax	(20)	(8)		(101)	(25)
Amortization of net unrealized (gains) losses on held to maturity securities, net of tax	9	8		21	18
Net change, before tax	64	72		656	476
Net change, tax	(17)	(19)		(172)	(125)
Net change, net of tax	47	53		484	351
Amortization of prior service credit, net of tax	(5)	(7)		(15)	(22)
Recognized net actuarial (gain) loss, net of tax	21	14	[1]	62	41
Net change, before tax	22	8		64	25
Net change, tax	(6)	(1)		(17)	(6)
Net change, net of tax	16	7		47	19
Other, before tax					1
Other, tax					0
Other Comprehensive Income, Other, Net of Tax					1
Other, net of tax	0	0		0	1
Other Comprehensive Income (Loss), before Tax	66	148		1,188	679
Other Comprehensive Income (Loss), Tax	(18)	(38)		(312)	(178)
Other Comprehensive Income (Loss), Net of Tax	48	110		876	501
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	20	(27)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	5	(7)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, before Tax	79	71
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax	21	18
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	27	11
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	7	3
Other Comprehensive Income Amortization of Net Unrealized Losses on Held To Maturity Securities Before Tax	(12)	(12)
Other Comprehensive Income Amortization of Net Unrealized Losses on Held To Maturity Securities Tax	(3)	(4)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	(6)	(10)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax	(1)	(3)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	(28)	(18)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax	$ (7)	$ (4)
Net Unrealized Gains (Losses) on Cash Flow Hedges
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax				477	110
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax				(9)	67
Reclassification from AOCI, Current Period, Tax				2	(18)
Other Comprehensive Income (Loss) before Reclassifications, Tax				(125)	(29)
Accumulated Net Investment Gain (Loss) Arising During the Period, Attributable to Parent
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax				765	485
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax				(137)	(34)
Reclassification from AOCI, Current Period, Tax				36	9
Other Comprehensive Income (Loss) before Reclassifications, Tax				(201)	(127)
Accumulated Net Investment Gain (Loss), Held to Maturity Securities, Attributable to Parent
Change in accumulated other comprehensive loss balances:
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax				28	25
Reclassification from AOCI, Current Period, Tax				(7)	(7)
Foreign Currency Translation Adjustment
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), Net of Tax				0
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax				(20)	(30)
Other Comprehensive Income (Loss) before Reclassifications, Tax				5	8
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax				84	55
Other Comprehensive Income (Loss) before Reclassifications, Tax				$ (22)	$ (14)

[1] (Dollars in millions) BeforeTaxAmount TaxEffect Net ofTaxFor the Three Months Ended September 30, 2019 Cash flow hedge activities: Unrealized net gains (losses) on hedges arising during the period $41 $(11) $30Reclassification adjustment for net (gains) losses on hedges included in interest income for loans and interest expense on long-term debt 27 (7) 20Net change 68 (18) 50Securities: Unrealized holding gains (losses) arising during the period on securities available for sale 71 (18) 53Reclassification adjustment for net (gains) losses on securities available for sale included in securities gains, net (11) 3 (8)Amortization of net unrealized (gains) losses on held to maturity securities 12 (4) 8Net change 72 (19) 53Pension and other benefits: Amortization of prior service credit(1) (10) 3 (7) Recognized net actuarial (gain) loss(1) 18 (4) 14Net change 8 (1) 7Net change in AOCI $148 $(38) $110