Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions			3 Months Ended		9 Months Ended
	Jan. 01, 2020	Jan. 01, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Summary of Accounting and Financial Policies [Line Items]
Firm's revenues from contracts with clients subject to ASU 2014-09 as a percentage of firm's total non-interest revenues			45.00%	50.00%	45.00%	45.00%
Investment Banking revenues from contracts with clients subject to ASU 2014-09 as a percentage of firm's investment banking revenues			90.00%	90.00%	90.00%	90.00%
Investment management revenues from contracts with clients subject to ASU 2014-09 as a percentage of firm's investment management revenue			95.00%	95.00%	95.00%	95.00%
Cash and due from banks			$ 11,710		$ 11,710		$ 12,570
Interest-bearing deposits with banks			141,490		141,490		120,980
Cash segregated for regulatory and other purposes			22,100		22,100		22,780
Receivable from customers and counterparties			62,560		62,560		50,900
Receivables from brokers, dealers and clearing organizations			48,620		48,620		23,710
Firm's receivables from contracts with clients			2,650		2,650		2,270
Payables to customers and counterparties			176,410		176,410		170,210
Payables to brokers, dealers and clearing organizations			10,950		10,950		4,610
Lease liabilities			$ 2,268		2,268		$ 2,385
Maximum [Member]
Summary of Accounting and Financial Policies [Line Items]
Annual average revenues associated with known remaining performance obligations					$ 250
Accounting Standards Update 2016-02 [Member]
Summary of Accounting and Financial Policies [Line Items]
Lease liabilities		$ 1,770
Accounting Standards Update 2016-02 [Member] | Revision of Prior Period, Change in Accounting Principle, Adjustment [Member]
Summary of Accounting and Financial Policies [Line Items]
New accounting standards impact on retained earnings		$ 12
Accounting Standards Update 2016-13 [Member] | Revision of Prior Period, Change in Accounting Principle, Adjustment [Member]
Summary of Accounting and Financial Policies [Line Items]
New accounting standards impact on retained earnings	$ 638
Accounting Standards Update 2016-13 [Member] | Maximum [Member]
Summary of Accounting and Financial Policies [Line Items]
Allowance for credit losses	848
Accounting Standards Update 2016-13 [Member] | Minimum [Member]
Summary of Accounting and Financial Policies [Line Items]
Allowance for credit losses	$ 169