Accumulated Other Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), before Tax, beginning balance	$ (442)	$ 506
Unrealized net gain on securities	170	(113)
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	1	(2)
Unrealized net gain on derivatives	23	1
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax	(102)	(114)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Tax	49	32
Accumulated Other Comprehensive Income (Loss), before Tax, ending balance	(301)	310
Accumulated Other Comprehensive Income Loss Tax [Abstract]
AOCI, beginning balance	153	(197)
Unrealized net gain on securities	(63)	41
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax	0	1
Unrealized net gain on derivatives	(9)	(1)
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Tax	38	43
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	(18)	(12)
AOCI, ending balance	101	(125)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
AOCI, beginning balance	(289)	309
Unrealized net gain on securities	107	(72)
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax	1	(1)
Unrealized net gain on derivatives	14	0
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	(64)	(71)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	31	20
AOCI, ending balance	$ (200)	$ 185