Fair Value - Partnership's Financial Assets and Liabilities at Fair Value (Detail) - USD ($) $ in Millions		Sep. 29, 2023	Dec. 31, 2022	Sep. 30, 2022
Cash equivalents:
Total cash equivalents		$ 677	$ 193
Investments segregated under federal regulations:
Total investments segregated under federal regulations		10,193	11,327	$ 12,653
Investment securities:
Total investment securities		1,228	1,329
Inventory securities:
Total inventory securities		125	76
Other Assets:
Client Fractional Shares Ownership Assets		731	680
Accounts payable, accrued expenses and other:
Client Fractional Shares Redemption Obligations		731	680
Equities [Member]
Investment securities:
Total investment securities		10	8
Inventory securities:
Total inventory securities		23	20
Corporate Bonds and Notes [Member]
Inventory securities:
Total inventory securities		10	21
Government and Agency Obligations [Member]
Investment securities:
Total investment securities		781	1,000
Inventory securities:
Total inventory securities		2	3
U.S. Treasuries [Member]
Investments segregated under federal regulations:
Total investments segregated under federal regulations		8,693	10,327
Mutual Funds [Member]
Investment securities:
Total investment securities	[1]	314	310
Inventory securities:
Total inventory securities		54	4
Municipal Obligations [Member]
Investment securities:
Total investment securities		23	11
Inventory securities:
Total inventory securities		31	28
Certificates of Deposit [Member]
Cash equivalents:
Total cash equivalents		614	144
Investments segregated under federal regulations:
Total investments segregated under federal regulations		1,500	1,000
Investment securities:
Total investment securities		100
Inventory securities:
Total inventory securities		5
Money Market Funds [Member]
Cash equivalents:
Total cash equivalents		63	49
Level I [Member]
Cash equivalents:
Total cash equivalents		63	49
Investments segregated under federal regulations:
Total investments segregated under federal regulations		8,693	10,327
Investment securities:
Total investment securities		1,105	1,318
Inventory securities:
Total inventory securities		79	27
Other Assets:
Client Fractional Shares Ownership Assets		731	680
Accounts payable, accrued expenses and other:
Client Fractional Shares Redemption Obligations		731	680
Level I [Member] | Equities [Member]
Investment securities:
Total investment securities		10	8
Inventory securities:
Total inventory securities		23	20
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		781	1,000
Inventory securities:
Total inventory securities		2	3
Level I [Member] | U.S. Treasuries [Member]
Investments segregated under federal regulations:
Total investments segregated under federal regulations		8,693	10,327
Level I [Member] | Mutual Funds [Member]
Investment securities:
Total investment securities	[1]	314	310
Inventory securities:
Total inventory securities		54	4
Level I [Member] | Municipal Obligations [Member]
Investment securities:
Total investment securities		0	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 [Member]
Cash equivalents:
Total cash equivalents		63	49
Level II [Member]
Cash equivalents:
Total cash equivalents		614	144
Investments segregated under federal regulations:
Total investments segregated under federal regulations		1,500	1,000
Investment securities:
Total investment securities		123	11
Inventory securities:
Total inventory securities		46	49
Other Assets:
Client Fractional Shares Ownership Assets		0	0
Accounts payable, accrued expenses and other:
Client Fractional Shares 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		10	21
Level II [Member] | Government and Agency Obligations [Member]
Investment securities:
Total investment securities		0	0
Inventory securities:
Total inventory securities		0	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	[1]	0	0
Inventory securities:
Total inventory securities		0	0
Level II [Member] | Municipal Obligations [Member]
Investment securities:
Total investment securities		23	11
Inventory securities:
Total inventory securities		31	28
Level II [Member] | Certificates of Deposit [Member]
Cash equivalents:
Total cash equivalents		614	144
Investments segregated under federal regulations:
Total investments segregated under federal regulations		1,500	1,000
Investment securities:
Total investment securities		100
Inventory securities:
Total inventory securities		5
Level II [Member] | Money Market Funds [Member]
Cash equivalents:
Total cash equivalents		0	0
Level III [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	0
Inventory securities:
Total inventory securities		0	0
Other Assets:
Client Fractional Shares Ownership Assets		0	0
Accounts payable, accrued expenses and other:
Client Fractional Shares Redemption Obligations		0	0
Level III [Member] | Equities [Member]
Investment securities:
Total investment securities		0	0
Inventory securities:
Total inventory securities		0	0
Level III [Member] | Corporate Bonds and Notes [Member]
Inventory securities:
Total inventory securities		0	0
Level III [Member] | Government and Agency Obligations [Member]
Investment securities:
Total investment securities		0	0
Inventory securities:
Total inventory securities		0	0
Level III [Member] | U.S. Treasuries [Member]
Investments segregated under federal regulations:
Total investments segregated under federal regulations		0	0
Level III [Member] | Mutual Funds [Member]
Investment securities:
Total investment securities	[1]	0	0
Inventory securities:
Total inventory securities		0	0
Level III [Member] | Municipal Obligations [Member]
Investment securities:
Total investment securities		0	0
Inventory securities:
Total inventory securities		0	0
Level III [Member] | Certificates of Deposit [Member]
Cash equivalents:
Total cash equivalents			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 III [Member] | Money Market Funds [Member]
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.