Loans - Impaired Commercial Loans Considered as TDR Loans (Detail) (Commercial Loans [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	$ 92		$ 165
Amount without Impairment Reserves	203		316
Total Impaired Commercial Loans	295	[1],[2]	481	[1],[2]
Impairment Reserve	30		40
Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	18		122
Amount without Impairment Reserves	179		211
Total Impaired Commercial Loans	197	[1],[2]	333	[1],[2]
Impairment Reserve	5		32
Business and Corporate Banking [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	72		28
Amount without Impairment Reserves	18		12
Total Impaired Commercial Loans	90	[1],[2]	40	[1],[2]
Impairment Reserve	24		3
Global Banking [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	0		14
Amount without Impairment Reserves	0		51
Total Impaired Commercial Loans	0	[1],[2]	65	[1],[2]
Impairment Reserve	0		5
Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	2		1
Amount without Impairment Reserves	6		42
Total Impaired Commercial Loans	8	[1],[2]	43	[1],[2]
Impairment Reserve	$ 1		$ 0

[1] Includes impaired commercial loans that are also considered TDR Loans which totaled $210 million and $389 million at December 31, 2014 and 2013, respectively.

[2] The impaired commercial loan balances included in the table above reflect the current carrying amount of the loan and includes all 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:At December 31,2014 2013 (in millions)Construction and other real estate$224 $380Business and corporate banking122 91Global banking— 123Other commercial8 47Total commercial$354 $641