Loans - Summary of TDR and Related Credit Loss Reserves for TDR Loans (Detail) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
TDR Loans	[1],[2],[3]	$ 1,249	$ 1,208
Allowance for credit losses on TDR Loans	[4]	49	56
Unpaid Principal Balance of TDR Loans		1,468	1,441
Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	[2],[3]	201	210
Allowance for credit losses on TDR Loans	[4]	6	9
Unpaid Principal Balance of TDR Loans		227	252
Commercial Loans [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	[2],[3]	120	186
Allowance for credit losses on TDR Loans	[4]	2	4
Unpaid Principal Balance of TDR Loans		139	201
Commercial Loans [Member] | Business and Corporate Banking [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	[2],[3]	68	24
Allowance for credit losses on TDR Loans	[4]	4	5
Unpaid Principal Balance of TDR Loans		75	51
Commercial Loans [Member] | Global Banking [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	[2],[3]	13	0
Unpaid Principal Balance of TDR Loans		13	0
Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	[2],[3]	1,048	998
Allowance for credit losses on TDR Loans	[4]	43	47
Unpaid Principal Balance of TDR Loans		1,241	1,189
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	[2],[3],[5]	1,021	972
Allowance for credit losses on TDR Loans	[4]	41	43
Unpaid Principal Balance of TDR Loans		1,189	1,139
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	[2],[3],[5]	21	20
Allowance for credit losses on TDR Loans	[4]	1	2
Unpaid Principal Balance of TDR Loans		46	44
Consumer Loans [Member] | Credit Cards [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	[2],[3]	6	6
Allowance for credit losses on TDR Loans	[4]	1	2
Unpaid Principal Balance of TDR Loans		$ 6	$ 6

[1] Includes $471 million and $485 million at June 30, 2015 and December 31, 2014, 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 $39 million and $85 million at June 30, 2015 and December 31, 2014, respectively.

[3] The TDR Loan balances included in the table above reflect the current carrying amount of TDR Loans and includes basis adjustments on the loan, such as unearned income, unamortized deferred fees and costs on originated loans, partial charge-offs and premiums or discounts on purchased loans. The following table reflects the unpaid principal balance of TDR Loans:June 30, 2015 December 31, 2014 (in millions)Commercial loans: Construction and other real estate$139 $201Business and corporate banking75 51Global banking13 —Total commercial227 252Consumer loans: Residential mortgages1,189 1,139 Home equity mortgages46 44Credit cards6 6Total consumer1,241 1,189Total$1,468 $1,441

[4] Included in the allowance for credit losses.

[5] Includes $775 million and $763 million at June 30, 2015 and December 31, 2014, respectively, of loans that are recorded at the lower of amortized cost or fair value of the collateral less cost to sell.