Accumulated Other Comprehensive Income - Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2011		Dec. 31, 2012
Unrealized gains (losses) on securities available-for-sale:
Balance at beginning of period	$ 257		$ 1,004		$ 992		$ 883
Other comprehensive income for period:
Net unrealized gains (losses) arising during period, net of tax of $(13) million and $89 million for the three months ended, $(468) million and $217 million for the nine months ended, respectively	(29)		126		(679)		303
Reclassification adjustment for gains realized in net income (loss), net of tax of $(14) million and $(20) million for the three months ended, $(75) million and $(60) million for the nine months ended, respectively	(21)	[1]	(29)	[1]	(106)	[1]	(85)	[1]
Total other comprehensive loss for period	(50)	[2]	97	[2]	(785)	[2]	218	[2]
Balance at end of period	207		1,101		207		1,101		883
Unrealized losses on other-than-temporarily impaired debt securities held-to-maturity:
Balance at beginning of period	(67)		0		0		0
Reclassification adjustment related to the accretion of unrealized other-than-temporary impairment, net of tax of $1 million for the three months ended and $(48) million for the nine months ended 2013					(67)		0
Reclassification adjustment related to the accretion of unrealized other-than-temporary impairment, net of tax of $1 million	2	[3]	0	[3]	2	[3]			0	[3]
Total other comprehensive income for period	(2)		0		(2)				0
Balance at end of period	(65)		0		(65)		0		0
Unrealized (losses) gains on derivatives classified as cash flow hedges:
Balance at beginning of period	(127)		(229)		(201)		(229)
Other comprehensive income (loss) for period:
Net gains (losses) arising during period, net of tax of $14 million and $5 million for the three months ended, and $63 million and $0 million for the nine months ended, respectively	20		9		90		4
Reclassification adjustment for losses realized in net income (loss), net of tax of $1 million and $2 million for the three months ended, and $4 million and $5 million for the nine months ended, respectively	1	[4]	2	[4]	5	[4]	7	[4]
Total other comprehensive income (loss) for period	21		11		95		11
Balance at end of period	(106)		(218)		(106)		(218)		(229)
Pension and postretirement benefit liability:
Balance at beginning of period	(6)		(11)		(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 for the three and nine months ended	1	[5]	0	[5]	1	[5]	1	[5]
Total other comprehensive income for period	1		0		1		1
Balance at end of period	(5)		(11)		(5)		(11)		(12)
Total accumulated other comprehensive income at end of period	$ 31		$ 872		$ 31		$ 872				$ 785

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

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

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

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

[5] Amount reclassified to net income (loss) is included in salaries and employee benefits in our consolidated statement of income (loss).