Accumulated Other Comprehensive Income - Accumulated Other Comprehensive Income by Component (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
AOCI net of tax, beginning balance	$ (507)	$ (95)
Other comprehensive income (loss) before reclassifications		286
Amounts reclassified out of AOCI		(3)
Other comprehensive income (loss)	(499)	283
AOCI net of tax, ending balance	(1,006)	188
Accumulated Other Comprehensive Income (Loss)
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
AOCI net of tax, beginning balance	(507)
Other comprehensive income (loss) before reclassifications	(504)
Amounts reclassified out of AOCI	5
Other comprehensive income (loss)	(499)
AOCI net of tax, ending balance	(1,006)
Net Unrealized Gains (Losses) on Cash Flow Hedges
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
AOCI net of tax, beginning balance	276	161
Other comprehensive income (loss) before reclassifications	11	(8)
Amounts reclassified out of AOCI	1	1
Other comprehensive income (loss)	12	(7)
AOCI net of tax, ending balance	288	154
Net Unrealized Gains (Losses) on Available-for-Sale Securities
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
AOCI net of tax, beginning balance	192	(221)
Other comprehensive income (loss) before reclassifications	179	258
Amounts reclassified out of AOCI	0	(9)
Other comprehensive income (loss)	179	249
AOCI net of tax, ending balance	371	28
Net Unrealized Losses on Hedges of Net Investments in Non-U.S. Subsidiaries
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
AOCI net of tax, beginning balance	(14)	(14)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified out of AOCI	0	0
Other comprehensive income (loss)	0	0
AOCI net of tax, ending balance	(14)	(14)
Other-Than-Temporary Impairment on Held-to-Maturity Securities
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
AOCI net of tax, beginning balance	(29)	(47)
Other comprehensive income (loss) before reclassifications	5	8
Amounts reclassified out of AOCI	(1)	0
Other comprehensive income (loss)	4	8
AOCI net of tax, ending balance	(25)	(39)
Net Unrealized Losses on Retirement Plans
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
AOCI net of tax, beginning balance	(272)	(203)
Other comprehensive income (loss) before reclassifications	0	1
Amounts reclassified out of AOCI	5	5
Other comprehensive income (loss)	5	6
AOCI net of tax, ending balance	(267)	(197)
Foreign Currency Translation
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
AOCI net of tax, beginning balance	(660)	229
Other comprehensive income (loss) before reclassifications	(699)	27
Amounts reclassified out of AOCI	0	0
Other comprehensive income (loss)	(699)	27
AOCI net of tax, ending balance	$ (1,359)	$ 256