Guarantee Arrangements and Pledged Assets - Summary of Credit Ratings of Credit Risk Related Guarantees (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	245,980
Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	237,548
Investment Grade [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	200,453
Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	193,318
Non-Investment Grade [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	45,527
Non-Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	44,230
Single name CDS [Member]
Credit Derivatives [Line Items]
Average Life in years	2 years 6 months	[1]
Single name CDS [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	162,794	[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	126,628	[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	36,166	[1]
Structured CDS [Member]
Credit Derivatives [Line Items]
Average Life in years	1 year 10 months 24 days	[1]
Structured CDS [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	34,926	[1]
Structured CDS [Member] | Investment Grade [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	31,540	[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	3,386	[1]
Index credit derivatives [Member]
Credit Derivatives [Line Items]
Average Life in years	3 years 4 months 24 days	[1]
Index credit derivatives [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	24,277	[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	23,741	[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	536	[1]
Total return swaps [Member]
Credit Derivatives [Line Items]
Average Life in years	6 years 8 months 12 days	[1]
Total return swaps [Member] | Sell-protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	15,551	[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	11,409	[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	4,142	[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	8,432	[2]
Standby Letters of Credit [Member] | Investment Grade [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	7,135	[2]
Standby Letters of Credit [Member] | Non-Investment Grade [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	1,297	[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.