Accumulated Other Comprehensive Income - Change in AOCI Gain (Loss) by Component (Net of Tax) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	$ (371)	$ (792)	$ (872)	$ 739
Other comprehensive income (loss) before reclassifications	(180)	(42)	345	(1,555)
Net realized (gains) losses reclassified from AOCI into earnings	(8)	(5)	(32)	(23)
Other comprehensive income (loss), net of tax	(188)	(47)	313	(1,578)
AOCI ending balance	(559)	(839)	(559)	(839)
Accumulated Net Unrealized Investment Gain (Loss) | Securities Available for Sale
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	419	(517)	106	703
Other comprehensive income (loss) before reclassifications	(62)	692	259	(526)
Net realized (gains) losses reclassified from AOCI into earnings	(3)	0	(11)	(2)
Other comprehensive income (loss), net of tax	(65)	692	248	(528)
AOCI ending balance	354	175	354	175
Accumulated Net Unrealized Investment Gain (Loss) | Securities Held to Maturity
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	(863)	0	(897)	0
Other comprehensive income (loss) before reclassifications	0	(916)	0	(916)
Net realized (gains) losses reclassified from AOCI into earnings	22	1	56	1
Other comprehensive income (loss), net of tax	22	(915)	56	(915)
AOCI ending balance	(841)	(915)	(841)	(915)
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	(20)	(129)	(110)	45
Other comprehensive income (loss) before reclassifications	(39)	59	96	(98)
Net realized (gains) losses reclassified from AOCI into earnings	(29)	(6)	(74)	(23)
Other comprehensive income (loss), net of tax	(68)	53	22	(121)
AOCI ending balance	(88)	(76)	(88)	(76)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	106	(111)	40	32
Other comprehensive income (loss) before reclassifications	(82)	124	(16)	(19)
Net realized (gains) losses reclassified from AOCI into earnings	0	0	0	0
Other comprehensive income (loss), net of tax	(82)	124	(16)	(19)
AOCI ending balance	24	13	24	13
Other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	(13)	(35)	(11)	(41)
Other comprehensive income (loss) before reclassifications	3	(1)	6	4
Net realized (gains) losses reclassified from AOCI into earnings	2	0	(3)	1
Other comprehensive income (loss), net of tax	5	(1)	3	5
AOCI ending balance	$ (8)	$ (36)	$ (8)	$ (36)