Regulation and Capital Adequacy - Risk-weighted Assets Rollforward (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Standardized Capital Rules [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk-Weighted Assets, Beginning balance	$ 524,107	$ 619,216
Change in deductions due to transitional provisions	(531)	(1,073)
Change in Credit RWAs	815	(52,577)
Change in Market RWAs	(11,902)	(42,532)
Risk-Weighted Assets, end of period	513,020	524,107
Standardized Capital Rules [Member] | Derivatives [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	(10,109)	(43,930)
Standardized Capital Rules [Member] | Commitments Guarantees and Loans [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	5,575	21,608
Standardized Capital Rules [Member] | Securities Financing Transactions [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	6,658	(20,724)
Standardized Capital Rules [Member] | Equity Investments [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	3,267	131
Standardized Capital Rules [Member] | Other [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	(4,045)	(8,589)
Standardized Capital Rules [Member] | Regulatory VaR [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(2,475)	1,762
Standardized Capital Rules [Member] | Stressed VaR [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	3,187	(7,887)
Standardized Capital Rules [Member] | Incremental Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(325)	(7,437)
Standardized Capital Rules [Member] | Comprehensive Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(87)	(4,130)
Standardized Capital Rules [Member] | Specific Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(12,202)	(24,840)
Basel III Advanced Transitional [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk-Weighted Assets, Beginning balance	577,651	570,313
Change in deductions due to transitional provisions	(531)	(1,073)
Change in Credit RWAs	18,527	16,138
Change in Market RWAs	(11,719)	(41,900)
Change in operational risk	(4,463)	33,100
Change in Operational RWAs	(4,463)	33,100
Risk-Weighted Assets, end of period	579,996	577,651
Basel III Advanced Transitional [Member] | Derivatives [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	10,249	(8,830)
Basel III Advanced Transitional [Member] | Commitments Guarantees and Loans [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	2,059	19,314
Basel III Advanced Transitional [Member] | Securities Financing Transactions [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	1,962	(717)
Basel III Advanced Transitional [Member] | Equity Investments [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	3,382	934
Basel III Advanced Transitional [Member] | Other [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	1,406	6,510
Basel III Advanced Transitional [Member] | Regulatory VaR [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(2,475)	1,762
Basel III Advanced Transitional [Member] | Stressed VaR [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	3,187	(7,887)
Basel III Advanced Transitional [Member] | Incremental Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(325)	(7,437)
Basel III Advanced Transitional [Member] | Comprehensive Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	96	(3,433)
Basel III Advanced Transitional [Member] | Specific Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	$ (12,202)	$ (24,905)