Loans - Impaired Commercial Loans Considered as TDR Loans (Detail) (Commercial Loan [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	$ 131		$ 250
Amount without Impairment Reserves	401		447
Total Impaired Commercial Loans	532	[1],[2],[3]	697	[1],[2],[3]
Impairment Reserve	35		96
Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	101		192
Amount without Impairment Reserves	292		305
Total Impaired Commercial Loans	393	[1],[2],[3]	497	[1],[2],[3]
Impairment Reserve	27		86
Business Banking and Middle Markets Enterprises [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	20		57
Amount without Impairment Reserves	27		49
Total Impaired Commercial Loans	47	[1],[2],[3]	106	[1],[2],[3]
Impairment Reserve	8		10
Global Banking [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	0		0
Amount without Impairment Reserves	18		18
Total Impaired Commercial Loans	18	[1],[2],[3]	18	[1],[2],[3]
Impairment Reserve	0		0
Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves	10		1
Amount without Impairment Reserves	64		75
Total Impaired Commercial Loans	74	[1],[2],[3]	76	[1],[2],[3]
Impairment Reserve	$ 0		$ 0

[1] The reduction in impaired commercial loans for construction and other real estate loans primarily relates to the charge-off of a single loan totaling $57 million in the first quarter of 2013 for which we were fully reserved.

[2] Includes impaired commercial loans which are also considered TDR Loans as follows: March 31, 2013 December 31, 2012 (in millions)Construction and other real estate$297 $343Business and corporate banking34 86Other commercial30 31Total$361 $460

[3] 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 unamortized deferred fees and costs on originated loans and any premiums or discounts. The unpaid principal balance of impaired commercial loans included in the table above are as follows:March 31, 2013 December 31, 2012 (in millions)Construction and other real estate$414 $552Business and corporate banking86 157Global banking18 18Other commercial77 79Total$595 $806