Receivables and Revenue - Schedule of Partnership's Disaggregated Revenue (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 28, 2025	Mar. 29, 2024
Disaggregation Of Revenue [Line Items]
Total revenue from customers	$ 3,923	$ 3,524
Net interest and dividends and other revenue	244	270
Net revenue	4,167	3,794
United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	3,828	3,436
Net interest and dividends and other revenue	219	252
Net revenue	4,047	3,688
Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	95	88
Net interest and dividends and other revenue	25	18
Net revenue	120	106
Total Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	3,480	3,100
Total Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	3,402	3,027
Total Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	78	73
Asset-based Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	3,294	2,908
Asset-based Fee Revenue [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	2,545	2,190
Asset-based Fee Revenue [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	410	392
Asset-based Fee Revenue [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Total revenue from customers	145	150
Asset-based Fee Revenue [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	194	176
Asset-based Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	3,219	2,839
Asset-based Fee Revenue [Member] | United States [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	2,496	2,146
Asset-based Fee Revenue [Member] | United States [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	384	367
Asset-based Fee Revenue [Member] | United States [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Total revenue from customers	145	150
Asset-based Fee Revenue [Member] | United States [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	194	176
Asset-based Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	75	69
Asset-based Fee Revenue [Member] | Canada [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	49	44
Asset-based Fee Revenue [Member] | Canada [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	26	25
Asset-based Fee Revenue [Member] | Canada [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Total revenue from customers	0	0
Asset-based Fee Revenue [Member] | Canada [Member] | Other Asset-based 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	186	192
Account and Activity Fee Revenue [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	118	116
Account and Activity Fee Revenue [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	68	76
Account and Activity Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	183	188
Account and Activity Fee Revenue [Member] | United States [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	118	116
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	65	72
Account and Activity Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	3	4
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	3	4
Trade Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	443	424
Trade Revenue [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	384	370
Trade Revenue [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	59	54
Trade Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	426	409
Trade Revenue [Member] | United States [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	370	358
Trade Revenue [Member] | United States [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	56	51
Trade Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	17	15
Trade Revenue [Member] | Canada [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	14	12
Trade Revenue [Member] | Canada [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from customers	$ 3	$ 3