Fair Value - Partnership's Financial Assets and Liabilities at Fair Value (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 25, 2022
Cash equivalents:
Total cash equivalents	$ 349	$ 193
Investments segregated under federal regulations:
Total investments segregated under federal regulations	11,067	11,327	$ 14,835
Investment securities:
Total investment securities	823	1,329
Inventory securities:
Total inventory securities	75	76
Other Assets
Client Fractional Shares Ownership Assets	710	680
Accounts payable, accrued expenses and other:
Client Fractional Shares Redemption Obligations	710	680
Equities [Member]
Investment securities:
Total investment securities	8	8
Inventory securities:
Total inventory securities	29	20
Corporate Bonds and Notes [Member]
Inventory securities:
Total inventory securities	4	21
Government and Agency Obligations [Member]
Investment securities:
Total investment securities	400	1,000
Inventory securities:
Total inventory securities	1	3
U.S. Treasuries [Member]
Investments segregated under federal regulations:
Total investments segregated under federal regulations	9,567	10,327
Mutual Funds [Member]
Investment securities:
Total investment securities	304	310
Inventory securities:
Total inventory securities	3	4
Municipal Obligations [Member]
Investment securities:
Total investment securities	11	11
Inventory securities:
Total inventory securities	33	28
Certificates of Deposit [Member]
Cash equivalents:
Total cash equivalents	336	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 Fund [Member]
Cash equivalents:
Total cash equivalents	13	49
Level I [Member]
Cash equivalents:
Total cash equivalents	13	49
Investments segregated under federal regulations:
Total investments segregated under federal regulations	9,567	10,327
Investment securities:
Total investment securities	712	1,318
Inventory securities:
Total inventory securities	33	27
Other Assets
Client Fractional Shares Ownership Assets	710	680
Accounts payable, accrued expenses and other:
Client Fractional Shares Redemption Obligations	710	680
Level I [Member] | Equities [Member]
Investment securities:
Total investment securities	8	8
Inventory securities:
Total inventory securities	29	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	400	1,000
Inventory securities:
Total inventory securities	1	3
Level I [Member] | U.S. Treasuries [Member]
Investments segregated under federal regulations:
Total investments segregated under federal regulations	9,567	10,327
Level I [Member] | Mutual Funds [Member]
Investment securities:
Total investment securities	304	310
Inventory securities:
Total inventory securities	3	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 Fund [Member]
Cash equivalents:
Total cash equivalents	13	49
Level II [Member]
Cash equivalents:
Total cash equivalents	336	144
Investments segregated under federal regulations:
Total investments segregated under federal regulations	1,500	1,000
Investment securities:
Total investment securities	111	11
Inventory securities:
Total inventory securities	42	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	4	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	0	0
Inventory securities:
Total inventory securities	0	0
Level II [Member] | Municipal Obligations [Member]
Investment securities:
Total investment securities	11	11
Inventory securities:
Total inventory securities	33	28
Level II [Member] | Certificates of Deposit [Member]
Cash equivalents:
Total cash equivalents	336	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 Fund [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	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	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 Fund [Member]
Cash equivalents:
Total cash equivalents	$ 0	$ 0