Receivables and Revenue - Schedule of Partnership's Disaggregated Revenue (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 29, 2024	Mar. 31, 2023
Disaggregation Of Revenue [Line Items]
Total revenue from customers	$ 3,524	$ 3,025
Net interest and dividends and other revenue	270	260
Net revenue	3,794	3,285
United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	3,436	2,948
Net interest and dividends and other revenue	252	242
Net revenue	3,688	3,190
Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	88	77
Net interest and dividends and other revenue	18	18
Net revenue	106	95
Total Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	3,100	2,685
Total Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	3,027	2,620
Total Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	73	65
Asset-based Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	2,908	2,501
Asset-based Fee Revenue [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	2,190	1,847
Asset-based Fee Revenue [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	392	361
Asset-based Fee Revenue [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	176	158
Asset-based Fee Revenue [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Total revenue from customers	150	135
Asset-based Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	2,839	2,439
Asset-based Fee Revenue [Member] | United States [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	2,146	1,810
Asset-based Fee Revenue [Member] | United States [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	367	336
Asset-based Fee Revenue [Member] | United States [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	176	158
Asset-based Fee Revenue [Member] | United States [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Total revenue from customers	150	135
Asset-based Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	69	62
Asset-based Fee Revenue [Member] | Canada [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	44	37
Asset-based Fee Revenue [Member] | Canada [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	25	25
Asset-based Fee Revenue [Member] | Canada [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	0	0
Asset-based Fee Revenue [Member] | Canada [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Total revenue from customers	0	0
Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	192	184
Account and Activity Fee Revenue [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	116	115
Account and Activity Fee Revenue [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	76	69
Account and Activity Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	188	181
Account and Activity Fee Revenue [Member] | United States [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	116	115
Account and Activity Fee Revenue [Member] | United States [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	72	66
Account and Activity Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	4	3
Account and Activity Fee Revenue [Member] | Canada [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	0	0
Account and Activity Fee Revenue [Member] | Canada [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	4	3
Trade Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	424	340
Trade Revenue [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	370	288
Trade Revenue [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	54	52
Trade Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	409	328
Trade Revenue [Member] | United States [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	358	278
Trade Revenue [Member] | United States [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	51	50
Trade Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	15	12
Trade Revenue [Member] | Canada [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	12	10
Trade Revenue [Member] | Canada [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	$ 3	$ 2