Regulation and Capital Adequacy - Capital 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]
Common Equity Tier 1, Beginning balance	$ 71,363	$ 69,830
Change in common shareholders' equity	379	1,931
Change in deductions for transitional provisions	(839)	(1,368)
Change in deductions for goodwill and identifiable intangible assets, net of deferred tax liabilities	11	75
Change in deductions for investments in nonconsolidated financial institutions	669	1,059
Change in other adjustments	114	(164)
Common Equity Tier 1, Ending balance	71,697	71,363
Tier 1 Capital, Beginning balance	81,511	78,433
Change in deductions for transitional provisions	(558)	(1,073)
Change in deductions for investments in covered funds	(174)	(413)
Other net increase in CET1	1,173	2,901
Redesignation of junior subordinated debt issued to trusts	(330)	(330)
Change in preferred stock	3	2,000
Change in other adjustments	119	(7)
Tier 1 Capital, Ending balance	81,744	81,511
Tier 2 capital, Beginning balance	16,705	12,861
Increased deductions for transitional provisions		(53)
Change in qualifying subordinated debt	(324)	3,238
Redesignation of junior subordinated debt issued to trusts	(198)	330
Change in the allowance for losses on loans and lending commitments	97	286
Change in other adjustments	15	43
Tier 2 Capital, Ending balance	16,295	16,705
Total capital	98,039	98,216
Basel III Advanced Transitional [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1, Beginning balance	71,363	69,830
Change in common shareholders' equity	379	1,931
Change in deductions for transitional provisions	(839)	(1,368)
Change in deductions for goodwill and identifiable intangible assets, net of deferred tax liabilities	11	75
Change in deductions for investments in nonconsolidated financial institutions	669	1,059
Change in other adjustments	114	(164)
Common Equity Tier 1, Ending balance	71,697	71,363
Tier 1 Capital, Beginning balance	81,511	78,433
Change in deductions for transitional provisions	(558)	(1,073)
Change in deductions for investments in covered funds	(174)	(413)
Other net increase in CET1	1,173	2,901
Redesignation of junior subordinated debt issued to trusts	(330)	(330)
Change in preferred stock	3	2,000
Change in other adjustments	119	(7)
Tier 1 Capital, Ending balance	81,744	81,511
Tier 2 capital, Beginning balance	16,103	12,545
Increased deductions for transitional provisions		(53)
Change in qualifying subordinated debt	(324)	3,238
Redesignation of junior subordinated debt issued to trusts	(198)	330
Change in other adjustments	15	43
Tier 2 Capital, Ending balance	15,596	16,103
Total capital	$ 97,340	$ 97,614