Fair Value - Partnership's Financial Assets and Liabilities at Fair Value (Detail) - USD ($) $ in Millions		Dec. 31, 2022	Dec. 31, 2021
Cash equivalents:
Total cash equivalents		$ 193	$ 313
Investments segregated under federal regulations:
Total investments segregated under federal regulations		11,327	14,308
Investment securities:
Total investment securities		1,329	852
Inventory securities:
Total inventory securities		76	38
Other assets:
Client fractional share ownership assets		680	710
Accounts payable, accrued expenses and other:
Client fractional share redemption obligations		680	710
Equities [Member]
Investment securities:
Total investment securities		8	3
Inventory securities:
Total inventory securities		20	18
Corporate Bonds and Notes [Member]
Inventory securities:
Total inventory securities		21	3
Government and Agency Obligations [Member]
Investment securities:
Total investment securities		1,000	413
Inventory securities:
Total inventory securities		3
U.S. Treasuries [Member]
Investments segregated under federal regulations:
Total investments segregated under federal regulations		10,327	13,908
Mutual Funds [Member]
Investment securities:
Total investment securities	[1]	310	366
Inventory securities:
Total inventory securities		4	2
Municipal Obligations [Member]
Investment securities:
Total investment securities		11
Inventory securities:
Total inventory securities		28	9
Certificates of Deposit [Member]
Cash equivalents:
Total cash equivalents		144	266
Investments segregated under federal regulations:
Total investments segregated under federal regulations		1,000	400
Investment securities:
Total investment securities			70
Inventory securities:
Total inventory securities			6
Money Market Funds
Cash equivalents:
Total cash equivalents		49	47
Level I [Member]
Cash equivalents:
Total cash equivalents		49	47
Investments segregated under federal regulations:
Total investments segregated under federal regulations		10,327	13,908
Investment securities:
Total investment securities		1,318	782
Inventory securities:
Total inventory securities		27	20
Other assets:
Client fractional share ownership assets		680	710
Accounts payable, accrued expenses and other:
Client fractional share redemption obligations		680	710
Level I [Member] | Equities [Member]
Investment securities:
Total investment securities		8	3
Inventory securities:
Total inventory securities		20	18
Level I [Member] | Corporate Bonds and Notes [Member]
Inventory securities:
Total inventory securities		0	0
Level I [Member] | Government and Agency Obligations [Member]
Investment securities:
Total investment securities		1,000	413
Inventory securities:
Total inventory securities		3
Level I [Member] | U.S. Treasuries [Member]
Investments segregated under federal regulations:
Total investments segregated under federal regulations		10,327	13,908
Level I [Member] | Mutual Funds [Member]
Investment securities:
Total investment securities	[1]	310	366
Inventory securities:
Total inventory securities		4	2
Level I [Member] | Municipal Obligations [Member]
Investment securities:
Total investment securities		0
Inventory securities:
Total inventory securities		0	0
Level I [Member] | Certificates of Deposit [Member]
Cash equivalents:
Total cash equivalents		0	0
Investments segregated under federal regulations:
Total investments segregated under federal regulations		0	0
Investment securities:
Total investment securities			0
Inventory securities:
Total inventory securities			0
Level I [Member] | Money Market Funds
Cash equivalents:
Total cash equivalents		49	47
Level II [Member]
Cash equivalents:
Total cash equivalents		144	266
Investments segregated under federal regulations:
Total investments segregated under federal regulations		1,000	400
Investment securities:
Total investment securities		11	70
Inventory securities:
Total inventory securities		49	18
Other assets:
Client fractional share ownership assets		0	0
Accounts payable, accrued expenses and other:
Client fractional share redemption obligations		0	0
Level II [Member] | Equities [Member]
Investment securities:
Total investment securities		0	0
Inventory securities:
Total inventory securities		0	0
Level II [Member] | Corporate Bonds and Notes [Member]
Inventory securities:
Total inventory securities		21	3
Level II [Member] | Government and Agency Obligations [Member]
Investment securities:
Total investment securities		0	0
Inventory securities:
Total inventory securities		0
Level II [Member] | U.S. Treasuries [Member]
Investments segregated under federal regulations:
Total investments segregated under federal regulations		0	0
Level II [Member] | Mutual Funds [Member]
Investment securities:
Total investment securities		0	0
Inventory securities:
Total inventory securities		0	0
Level II [Member] | Municipal Obligations [Member]
Investment securities:
Total investment securities		11
Inventory securities:
Total inventory securities		28	9
Level II [Member] | Certificates of Deposit [Member]
Cash equivalents:
Total cash equivalents		144	266
Investments segregated under federal regulations:
Total investments segregated under federal regulations		1,000	400
Investment securities:
Total investment securities			70
Inventory securities:
Total inventory securities			6
Level II [Member] | Money Market Funds
Cash equivalents:
Total cash equivalents		$ 0	$ 0

[1] The mutual funds balance consists primarily of securities held to economically hedge future liabilities for the non-qualified deferred compensation plan. The balance also includes a security held for regulatory purposes at the Trust Co.