Commitments and Contingent Liabilities- Significant Industry Concentrations Related to Credit Exposure (Detail) (USD $) In Billions, unless otherwise specified	Sep. 30, 2013
Financial institutions
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	$ 12.7
Unfunded commitments	16.0
Total exposure	28.7
Financial institutions | Banks
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	8.3
Unfunded commitments	2.0
Total exposure	10.3
Financial institutions | Asset Managers
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	1.2
Unfunded commitments	4.0
Total exposure	5.2
Financial institutions | Securities Industry
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	2.5
Unfunded commitments	1.5
Total exposure	4.0
Financial institutions | Insurance
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	0.1
Unfunded commitments	4.3
Total exposure	4.4
Financial institutions | Government
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	0.4
Unfunded commitments	3.0
Total exposure	3.4
Financial institutions | Other
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	0.2
Unfunded commitments	1.2
Total exposure	1.4
Commercial
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	1.6
Unfunded commitments	19.9
Total exposure	21.5
Commercial | Services and Other
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	0.6
Unfunded commitments	6.1
Total exposure	6.7
Commercial | Energy and Utilities
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	0.7
Unfunded commitments	6.1
Total exposure	6.8
Commercial | Manufacturing
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	0.3
Unfunded commitments	5.9
Total exposure	6.2
Commercial | Media and Telecom
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans	0
Unfunded commitments	1.8
Total exposure	$ 1.8