Loans - Impaired Commercial Loans Considered as TDR Loans (Detail) (Commercial Loans [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	$ 83		$ 92
Amount without Impairment Reserves	232		203
Total Impaired Commercial Loans	315	[1],[2]	295	[1],[2]
Impairment Reserve	27		30
Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	14		18
Amount without Impairment Reserves	185		179
Total Impaired Commercial Loans	199	[1],[2]	197	[1],[2]
Impairment Reserve	3		5
Business and Corporate Banking [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	68		72
Amount without Impairment Reserves	28		18
Total Impaired Commercial Loans	96	[1],[2]	90	[1],[2]
Impairment Reserve	23		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	13	[1],[2]	0	[1],[2]
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	7	[1],[2]	8	[1],[2]
Impairment Reserve	$ 1		$ 1

[1] 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:March 31, 2015 December 31, 2014 (in millions)Construction and other real estate$223 $224Business and corporate banking101 122Global banking13 —Other commercial7 8Total commercial$344 $354

[2] Includes impaired commercial loans that are also considered TDR Loans which totaled $236 million and $210 million at March 31, 2015 and December 31, 2014, respectively.