Guarantee Arrangements and Pledged Assets - Summary of Credit Ratings of Credit Risk Related Guarantees (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	237,318
Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	229,166
Investment Grade [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	203,108
Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	196,414
Non-Investment Grade [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	34,210
Non-Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	32,752
Single name CDS [Member]
Credit Derivatives [Line Items]
Average Life in years	2 years 4 months 24 days	[1]
Single name CDS [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	156,149	[1]
Single name CDS [Member] | Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	128,824	[1]
Single name CDS [Member] | Non-Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	27,325	[1]
Structured CDS [Member]
Credit Derivatives [Line Items]
Average Life in years	1 year 8 months 12 days	[1]
Structured CDS [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	34,038	[1]
Structured CDS [Member] | Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	30,714	[1]
Structured CDS [Member] | Non-Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	3,324	[1]
Index credit derivatives [Member]
Credit Derivatives [Line Items]
Average Life in years	3 years 3 months 18 days	[1]
Index credit derivatives [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	25,224	[1]
Index credit derivatives [Member] | Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	25,166	[1]
Index credit derivatives [Member] | Non-Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	58	[1]
Total return swaps [Member]
Credit Derivatives [Line Items]
Average Life in years	7 years 3 months 18 days	[1]
Total return swaps [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	13,755	[1]
Total return swaps [Member] | Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	11,710	[1]
Total return swaps [Member] | Non-Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	2,045	[1]
Standby Letters of Credit [Member]
Credit Derivatives [Line Items]
Average Life in years	1 year 3 months 18 days	[2]
Credit Ratings of the Obligors or the Transactions	8,152	[2]
Standby Letters of Credit [Member] | Investment Grade [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	6,694	[2]
Standby Letters of Credit [Member] | Non-Investment Grade [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	1,458	[2]

[1] The credit ratings in the table represent external credit ratings for classification as investment grade and non-investment grade.

[2] External ratings for most of the obligors are not available. Presented above are the internal credit ratings which are developed using similar methodologies and rating scale equivalent to external credit ratings for purposes of classification as investment grade and non-investment grade.