Accumulated Other Comprehensive Income - Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012
Unrealized gains (losses) on securities available-for-sale:
Balance at beginning of period	$ 842		$ 756		$ 992		$ 883
Other comprehensive income for period:
Net unrealized gains (losses) arising during period, net of tax of $(398) million and $203 million for the three months ended, $(455) million and $127 million for the six months ended, respectively	(571)		286		(649)		177
Reclassification adjustment for gains realized in net income (loss), net of tax of $(9) million and $(27) million for the three months ended, $(60) million and $(39) million for the six months ended, respectively	(14)	[1]	(38)	[1]	(86)	[1]	(56)	[1]
Total other comprehensive loss for period	(585)	[2]	248	[2]	(735)	[2]	121	[2]
Balance at end of period	257		1,004		257		1,004
Unrealized losses on other-than-temporarily impaired debt securities held-to-maturity:
Balance at beginning of period	0		0		0		0
Adjustment to add other-than-temporary impairment due to the consolidation of VIE, net of tax of $(48) million, for the three and six months ended	(67)		0		(67)		0
Balance at end of period	(67)		0		(67)		0
Unrealized (losses) gains on derivatives classified as cash flow hedges:
Balance at beginning of period	(178)		(192)		(201)		(229)
Other comprehensive income (loss) for period:
Net gains (losses) arising during period, net of tax of $35 million and $(29) million for the three months ended, and $49 million and $(5) million for the six months ended, respectively	49		(39)		70		(5)
Reclassification adjustment for losses realized in net income (loss), net of tax of $1 million and $2 million for the three months ended, and $3 million and $3 million, respectively	2	[3]	2	[3]	4	[3]	5	[3]
Total other comprehensive income (loss) for period	51		(37)		74		0
Balance at end of period	(127)		(229)		(127)		(229)
Pension and postretirement benefit liability:
Balance at beginning of period					(6)		(12)
Other comprehensive income (loss) for period:
Reclassification adjustment of prior service costs and transition obligations in net income, net of tax of less than $1 million					0		1
Total other comprehensive income for period	0		0		0		1
Balance at end of period	(6)		(11)		(6)		(11)
Total accumulated other comprehensive income at end of period	$ 57		$ 764		$ 57		$ 764		$ 785

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

[2] During the three and six months ended June 30, 2013 and 2012, there were no other-than-temporary impairment ("OTTI") losses on securities recognized in other revenues and no OTTI losses in the non-credit component of securities were recognized in accumulated other comprehensive income.

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