Loans - Impaired Commercial Loans Considered as TDR Loans - Additional Information (Detail) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
TDR Loans	[1],[2],[3]	$ 1,352	$ 1,208
Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	[2],[3]	$ 270	$ 210

[1] At September 30, 2015 and December 31, 2014, the carrying value reflected above includes $520 million and $485 million, respectively, of loans which are classified as nonaccrual.

[2] TDR Loans are considered to be impaired loans. For consumer loans, all such loans are considered impaired loans regardless of accrual status. For commercial loans, impaired loans include other loans in addition to TDR Loans which totaled $62 million and $85 million at September 30, 2015 and December 31, 2014, respectively.

[3] The carrying value of TDR Loans includes basis adjustments on the loans, such as unearned income, unamortized deferred fees and costs on originated loans, partial charge-offs and premiums or discounts on purchased loans.