Loans - Impaired Commercial Loans Considered as TDR Loans - Additional Information (Detail) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
TDR Loans	[1],[2],[3]	$ 1,416	$ 1,453
Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	[2],[3],[4]	$ 444	$ 365

[1] At March 31, 2016 and December 31, 2015, the carrying value of TDR Loans includes $622 million and $676 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 $269 million and $88 million at March 31, 2016 and December 31, 2015, 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.

[4] Additional commitments to lend to commercial borrowers whose loans have been modified in TDRs totaled $146 million and $112 million at March 31, 2016 and December 31, 2015, respectively.