Guarantees - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions	1 Months Ended
	May. 31, 2009	Jun. 30, 2015		Dec. 31, 2014	Jun. 30, 2014		Dec. 31, 2013
Business Combination, Contingent Consideration, Liability		$ 23		$ 27
Unpaid Principal Balance Of Unresolved Repurchase Requests		24	[1]	47	$ 52	[1]	$ 126
Standby Letters of Credit
Maximum potential amount obligation		3,000		3,000
Mortgage Servicing Rights [Member]
Loss Contingency Accrual, at Carrying Value		24		25
Visa Interest [Member]
Derivative Liability, Current		7		$ 5
Tax Credit Sales [Member]
Maximum potential amount obligation		19
Not Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member] | Visa Interest [Member]
Number Of Shares Sold To Selected Financial Institutions	3.2
Non-Government Sponsored Agency [Member]
Unpaid Principal Balance Of Unresolved Repurchase Requests		$ 1			$ 3

[1] 1 Comprised of $23 million and $49 million from the GSEs, and $1 million and $3 million from non-agency investors at June 30, 2015 and 2014, respectively.