Securities - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013 security	Jun. 30, 2012	Jun. 30, 2013 security	Jun. 30, 2012	Mar. 31, 2013 security	Dec. 31, 2012 security
Schedule of Available-for-sale Securities [Line Items]
Securities held-to-maturity	$ 1,538,000,000		$ 1,538,000,000			$ 1,620,000,000
Percentage of debt securities issued by US Treasury, US Government Agencies and government sponsored entities	88.00%		88.00%			90.00%
Temporary impairment losses recognized credit loss	0	0	0	0
Other-than-temporary securities accumulated impairment	115,000,000		115,000,000
Non-credit component unrealized loss amounts recognized			0
Assets backed securities in available for sale portfolio	26		26			27
Assets backed securities wrapped by monoline insurance company	8		8			8
Value of asset backed securites backed by insurance company	349,000,000		349,000,000			343,000,000
Fair value of asset backed securities	516,000,000		516,000,000			557,000,000
Available-for-sale securities, accumulated unrecognized holding loss	38,000,000		38,000,000			69,000,000
Fair value of financial guarantee	107,000,000		107,000,000			110,000,000
Security wrapped by below investment grade monoline insurance was deemed to be other-than-temporarily impaired	0		0			0
Assets backed securities in held for sale portfolio					6
Sold security at carrying value					71,000,000
Asset backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities held-to-maturity	218,000,000		218,000,000
Federal Home Loan Bank [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments in stock were included in other assets	139,000,000		139,000,000			143,000,000
Federal Reserve Bank [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments in stock were included in other assets	$ 482,000,000		$ 482,000,000			$ 483,000,000