Standby and Commercial Letters of Credit, Conditional Commitments Issued to Guarantee the Performance of a Customer to a Third Party (Parenthetical) (Detail) - Financial Standby Letter of Credit $ in Millions		Jun. 30, 2015 USD ($)
Line of Credit Facility [Line Items]
Commitments		$ 3,542
Less Than One Year From The Balance Sheet Date
Line of Credit Facility [Line Items]
Commitments	[1]	1,960
Less Than One Year From The Balance Sheet Date | Commercial
Line of Credit Facility [Line Items]
Commitments		47
More than One and within Five Years from Balance Sheet Date
Line of Credit Facility [Line Items]
Commitments	[1]	1,532
More than One and within Five Years from Balance Sheet Date | Commercial
Line of Credit Facility [Line Items]
Commitments		21
More than five years from balance sheet date
Line of Credit Facility [Line Items]
Commitments		$ 50

[1] Includes $47 and $21 issued on behalf of commercial customers to facilitate trade payments in U.S. dollars and foreign currencies which expire less than one year and between one and five years, respectively.