Accumulated Other Comprehensive Income - (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Unrealized gains (losses) on securities available-for-sale:
Balance at beginning of period	$ (18)		$ 992
Other comprehensive income for period:
Net unrealized gains (losses) arising during period, net of tax of $93 million and $(61) million, respectively	144		(82)
Reclassification adjustment for gains realized in net income, net of tax of $9 million and $(47) million, respectively	(14)	[1]	(68)	[1]
Total other comprehensive loss for period	130		(150)
Balance at end of period	112		842
Unrealized losses on other-than-temporarily impaired debt securities held-to-maturity:
Balance at beginning of period	(60)		0
Reclassification adjustment related to the accretion of unrealized other-than-temporary impairment, net of tax of $4 million	1	[2]	0	[2]
Total other comprehensive income for period	(1)		0
Balance at end of period	(59)		0
Unrealized (losses) gains on derivatives classified as cash flow hedges:
Balance at beginning of period	(83)		(201)
Other comprehensive income (loss) for period:
Net gains (losses) arising during period, net of tax of $(13) million and $13 million, respectively	(21)		21
Reclassification adjustment for losses realized in net income, net of tax of $ million and $2 million, respectively	1	[3]	2	[3]
Total other comprehensive income (loss) for period	(20)		23
Balance at end of period	(103)		(178)
Pension and postretirement benefit liability:
Balance at end of period	2		(6)
Total accumulated other comprehensive income (loss) at end of period	$ (48)		$ 658		$ (159)

[1] Amount reclassified to net income is included in other securities gains, net in our consolidated statement of income.

[2] Amount reclassified to the carrying value of the debt securities is included in securities held-to-maturity in our consolidated balance sheet.

[3] Amount reclassified to net income is included in interest income (expense) in our consolidated statement of income.