Loans - Impaired Commercial Loans Considered as TDR Loans (Detail) - Commercial Loans [Member] - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves		$ 27	$ 92
Amount without Impairment Reserves		213	203
Total Impaired Commercial Loans	[1],[2]	240	295
Impairment Reserve		7	30
Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves		13	18
Amount without Impairment Reserves		119	179
Total Impaired Commercial Loans	[1],[2]	132	197
Impairment Reserve		3	5
Business and Corporate Banking [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves		13	72
Amount without Impairment Reserves		75	18
Total Impaired Commercial Loans	[1],[2]	88	90
Impairment Reserve		3	24
Global Banking [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves		0	0
Amount without Impairment Reserves		13	0
Total Impaired Commercial Loans	[1],[2]	13	0
Impairment Reserve		0	0
Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves		1	2
Amount without Impairment Reserves		6	6
Total Impaired Commercial Loans	[1],[2]	7	8
Impairment Reserve		$ 1	$ 1

[1] Includes impaired commercial loans that are also considered TDR Loans which totaled $201 million and $210 million at June 30, 2015 and December 31, 2014, respectively.

[2] The impaired commercial loan balances included in the table above reflect the current carrying amount of the loan and includes basis adjustments, such as partial charge-offs, unamortized deferred fees and costs on originated loans and any premiums or discounts. The following table reflects the unpaid principal balance of impaired commercial loans included in the table above:June 30, 2015 December 31, 2014 (in millions)Construction and other real estate$156 $224Business and corporate banking120 122Global banking13 —Other commercial7 8Total commercial$296 $354