Guarantee Arrangements, Pledged Assets and Repurchase Agreements - Summary of Credit Ratings of Credit Risk Related Guarantees (Detail) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015	Dec. 31, 2014
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions		$ 114,532	$ 128,894
Credit Ratings of the Obligors or the Transactions, Total		111,435
Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions		$ 102,403
Single name credit default swap [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Average Life in years	[1]	2 years 6 months 12 days
Credit Ratings of the Obligors or the Transactions	[1]	$ 81,287
Structured CDS [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Average Life in years	[1]	1 year 7 months
Credit Ratings of the Obligors or the Transactions	[1]	$ 5,662
Index credit derivatives [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Average Life in years	[1]	3 years 2 months 25 days
Credit Ratings of the Obligors or the Transactions	[1]	$ 11,737
Total return swaps [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Average Life in years	[1]	2 years 4 months 11 days
Credit Ratings of the Obligors or the Transactions	[1]	$ 3,717
Standby Letters of Credit [Member]
Credit Derivatives [Line Items]
Average Life in years	[2]	1 year 17 days
Credit Ratings of the Obligors or the Transactions	[2]	$ 9,032
External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions, Total		83,474
External Credit Rating, Investment Grade [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions		77,162
External Credit Rating, Investment Grade [Member] | Single name credit default swap [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	[1]	64,937
External Credit Rating, Investment Grade [Member] | Structured CDS [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	[1]	5,046
External Credit Rating, Investment Grade [Member] | Index credit derivatives [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	[1]	3,864
External Credit Rating, Investment Grade [Member] | Total return swaps [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	[1]	3,315
External Credit Rating, Investment Grade [Member] | Standby Letters of Credit [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	[2]	6,312
External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions, Total		27,961
External Credit Rating, Non Investment Grade [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions		25,241
External Credit Rating, Non Investment Grade [Member] | Single name credit default swap [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	[1]	16,350
External Credit Rating, Non Investment Grade [Member] | Structured CDS [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	[1]	616
External Credit Rating, Non Investment Grade [Member] | Index credit derivatives [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	[1]	7,873
External Credit Rating, Non Investment Grade [Member] | Total return swaps [Member] | Sell Protection Credit Derivatives [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	[1]	402
External Credit Rating, Non Investment Grade [Member] | Standby Letters of Credit [Member]
Credit Derivatives [Line Items]
Credit Ratings of the Obligors or the Transactions	[2]	$ 2,720

[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.