Fair Value - Partnership's Financial Assets and Liabilities at Fair Value (Detail) - USD ($) $ in Millions		Sep. 27, 2024	Dec. 31, 2023
Cash equivalents:
Total cash equivalents		$ 236	$ 255
Investments segregated under federal regulations:
Total investments segregated under federal regulations		9,038	11,393
Securities owned:
Total investment securities		1,379	1,069
Inventory securities:
Total inventory securities		214	88
Other Assets:
Client Fractional Shares Ownership Assets		925	824
Accounts payable, accrued expenses and other:
Client Fractional Shares Redemption Obligations		925	824
Equities [Member]
Securities owned:
Total investment securities		8	11
Inventory securities:
Total inventory securities		19	21
Corporate Bonds and Notes [Member]
Inventory securities:
Total inventory securities		15	5
Government and Agency Obligations [Member]
Securities owned:
Total investment securities		895	600
Inventory securities:
Total inventory securities		15	4
U.S. Treasuries [Member]
Investments segregated under federal regulations:
Total investments segregated under federal regulations		7,938	9,893
Mutual Funds [Member]
Securities owned:
Total investment securities	[1]	364	346
Inventory securities:
Total inventory securities		103	9
Municipal Obligations [Member]
Securities owned:
Total investment securities		12	12
Inventory securities:
Total inventory securities		50	29
Certificates of deposit [Member]
Cash equivalents:
Total cash equivalents		163	179
Investments segregated under federal regulations:
Total investments segregated under federal regulations		1,100	1,500
Securities owned:
Total investment securities		100	100
Inventory securities:
Total inventory securities		12	20
Money Market Funds [Member]
Cash equivalents:
Total cash equivalents		73	76
Level I [Member]
Cash equivalents:
Total cash equivalents		73	76
Investments segregated under federal regulations:
Total investments segregated under federal regulations		7,938	9,893
Securities owned:
Total investment securities		1,267	957
Inventory securities:
Total inventory securities		137	34
Other Assets:
Client Fractional Shares Ownership Assets		925	824
Accounts payable, accrued expenses and other:
Client Fractional Shares Redemption Obligations		925	824
Level I [Member] | Equities [Member]
Securities owned:
Total investment securities		8	11
Inventory securities:
Total inventory securities		19	21
Level I [Member] | Corporate Bonds and Notes [Member]
Inventory securities:
Total inventory securities		0	0
Level I [Member] | Government and Agency Obligations [Member]
Securities owned:
Total investment securities		895	600
Inventory securities:
Total inventory securities		15	4
Level I [Member] | U.S. Treasuries [Member]
Investments segregated under federal regulations:
Total investments segregated under federal regulations		7,938	9,893
Level I [Member] | Mutual Funds [Member]
Securities owned:
Total investment securities	[1]	364	346
Inventory securities:
Total inventory securities		103	9
Level I [Member] | Municipal Obligations [Member]
Securities owned:
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
Securities owned:
Total investment securities		0	0
Inventory securities:
Total inventory securities		0	0
Level I [Member] | Money Market Funds [Member]
Cash equivalents:
Total cash equivalents		73	76
Level II [Member]
Cash equivalents:
Total cash equivalents		163	179
Investments segregated under federal regulations:
Total investments segregated under federal regulations		1,100	1,500
Securities owned:
Total investment securities		112	112
Inventory securities:
Total inventory securities		77	54
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]
Securities owned:
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		15	5
Level II [Member] | Government and Agency Obligations [Member]
Securities owned:
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]
Securities owned:
Total investment securities	[1]	0	0
Inventory securities:
Total inventory securities		0	0
Level II [Member] | Municipal Obligations [Member]
Securities owned:
Total investment securities		12	12
Inventory securities:
Total inventory securities		50	29
Level II [Member] | Certificates of deposit [Member]
Cash equivalents:
Total cash equivalents		163	179
Investments segregated under federal regulations:
Total investments segregated under federal regulations		1,100	1,500
Securities owned:
Total investment securities		100	100
Inventory securities:
Total inventory securities		12	20
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
Securities owned:
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]
Securities owned:
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]
Securities owned:
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]
Securities owned:
Total investment securities	[1]	0	0
Inventory securities:
Total inventory securities		0	0
Level III [Member] | Municipal Obligations [Member]
Securities owned:
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
Securities owned:
Total investment securities		0	0
Inventory securities:
Total inventory securities		0	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.