Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Foreign currency translation adjustment	$ 4	$ (7)
Unrealized net gains (losses) on hedges arising during the period, Before Tax Amount	266	119
Less: Reclassification adjustment for net (gains) losses on hedges included in interest income for loans and interest expense on long-term debt, Before Tax Amount	(43)	(33)
Net change, Before Tax Amount	223	86
Unrealized holding gains (losses) arising during the period on securities available for sale, Before Tax Amount	158	120
Reclassification adjustment for net (gains) losses on securities available for sale included in securities gains, net, Before Tax Amount	(13)	(3)
Less: accretion of fair value adjustment on securities available for sale, Before Tax Amount		(2)
Less: amortization of net unrealized (gains) losses on held to maturity securities, Before Tax Amount	5	5
Net change, Before Tax Amount	150	120
Foreign currency translation adjustment, Before Tax Amount	7	(12)
Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax	(6)	(6)
Recognized net actuarial (gain) loss, Before Tax Amount	22	29
Net change, Before Tax Amount	(16)	23
Net change in accumulated other comprehensive loss, Before Tax Amount	394	217
Unrealized net gains (losses) on hedges arising during the period, Tax Effect	(105)	(47)
Less: Reclassification adjustment for net (gains) losses on hedges included in interest income for loans and interest expense on long-term debt, Tax Effect	17	13
Net change, Tax Effect	88	(34)
Unrealized holding gains (losses) arising during the period on securities available for sale, Tax Effect	(62)	(47)
Reclassification adjustment for net (gains) losses on securities available for sale included in securities gains, net, Tax Effect	5	1
Less: accretion of fair value adjustment on securities available for sale, Tax Effect		1
Less: amortization of net unrealized (gains) losses on held to maturity securities, Tax Effect	(2)	(2)
Net change, Tax Effect	59	(47)
Foreign currency translation adjustment, Tax Effect	(3)	5
Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), Tax	3	2
Recognized net actuarial (gain) loss, Tax Effect	(9)	(11)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	13	18
Net change, Tax Effect	(6)	(9)
Net change in accumulated other comprehensive loss, Tax Effect	155	(85)
Unrealized net gains (losses) on hedges arising during the period, Net of Tax	161	72
Less: Reclassification adjustment for net (gains) losses on hedges included in interest income for loans and interest expense on long-term debt, Net of Tax	(26)	(20)
Net change, Net of Tax	135	52
Unrealized holding gains (losses) arising during the period on securities available for sale, Net of Tax	96	73
Reclassification adjustment for net (gains) losses on securities available for sale included in securities gains, net, Net of Tax	(8)	(2)
Less: accretion of fair value adjustment on securities available for sale, Net of Tax		(1)
Less: amortization of net unrealized (gains) losses on held to maturity securities, Net of Tax	3	3
Net change, Net of Tax	91	73
Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), Net of Tax	(3)	(4)
Net change, Net of Tax	10	14
Other Comprehensive Income Other Before Tax	(2)
Other Comprehensive Income Other Tax	1
Other Comprehensive Income, Other, Net of Tax	(1)
Total other comprehensive income (loss)	$ 239	$ 132