Loans - Summary of TDR and Related Credit Loss Reserves for TDR Loans - Additional Information (Detail) - USD ($)	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other loans included in impaired loans apart from TDR loans	$ 269,000,000	$ 88,000,000
Residential mortgage loan TDR carried at lower of amortized cost or fair value less cost to sell	771,000,000	881,000,000	$ 778,000,000
Non Accrual loans included in TDR loan	622,000,000	676,000,000
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additional commitments to lend to commercial borrowers with modified TDRs	146,000,000	$ 112,000,000
Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDRs transferred to held-for-sale, carrying value	130,000,000
Allowance for credit losses, loans held for sale	$ 0