Regulation and Capital Adequacy - Risk-weighted Assets Rollforward (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Standardized Capital Rules [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk-Weighted Assets, Beginning balance	$ 496,676	$ 524,107
Change in deductions due to transitional provisions	(233)	(531)
Change in Credit RWAs	12,373	(8,705)
Change in Market RWAs	(1,648)	(18,726)
Risk-Weighted Assets, end of period	507,401	496,676
Standardized Capital Rules [Member] | Derivatives [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	(3,529)	(12,555)
Standardized Capital Rules [Member] | Commitments Guarantees and Loans [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	3,039	4,353
Standardized Capital Rules [Member] | Securities Financing Transactions [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	7,492	(73)
Standardized Capital Rules [Member] | Equity Investments [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	1,800	4,196
Standardized Capital Rules [Member] | Other [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	3,804	(4,095)
Standardized Capital Rules [Member] | Regulatory VaR [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(112)	(2,250)
Standardized Capital Rules [Member] | Stressed VaR [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	3,688	737
Standardized Capital Rules [Member] | Incremental Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	1,325	(1,638)
Standardized Capital Rules [Member] | Comprehensive Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(675)	(387)
Standardized Capital Rules [Member] | Specific Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(5,874)	(15,188)
Basel III Advanced Transitional [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk-Weighted Assets, Beginning balance	549,650	577,651
Change in deductions due to transitional provisions	(233)	(531)
Change in Credit RWAs	10,693	6,005
Change in Market RWAs	(1,510)	(18,506)
Change in operational risk	(557)	(15,500)
Change in Operational RWAs	(557)	(15,500)
Risk-Weighted Assets, end of period	558,276	549,650
Basel III Advanced Transitional [Member] | Derivatives [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	(5,387)	(8,575)
Basel III Advanced Transitional [Member] | Commitments Guarantees and Loans [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	8,171	8,269
Basel III Advanced Transitional [Member] | Securities Financing Transactions [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	2,813	(228)
Basel III Advanced Transitional [Member] | Equity Investments [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	1,961	4,440
Basel III Advanced Transitional [Member] | Other [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Credit RWAs	3,368	2,630
Basel III Advanced Transitional [Member] | Regulatory VaR [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(112)	(2,250)
Basel III Advanced Transitional [Member] | Stressed VaR [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	3,688	737
Basel III Advanced Transitional [Member] | Incremental Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	1,325	(1,638)
Basel III Advanced Transitional [Member] | Comprehensive Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	(537)	(167)
Basel III Advanced Transitional [Member] | Specific Risk [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Change in Market RWAs	$ (5,874)	$ (15,188)