Revenue - Schedule of Partnership's Disaggregated Revenue (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Disaggregation Of Revenue [Line Items]
Net revenue	$ 2,099	$ 1,989
Net interest and dividends and other revenue	91	53
Net revenue	2,190	2,042
United States [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	2,048	1,935
Net interest and dividends and other revenue	87	49
Net revenue	2,135	1,984
Canada [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	51	54
Net interest and dividends and other revenue	4	4
Net revenue	55	58
Asset-based Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	1,559	1,453
Asset-based Fee Revenue [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	1,096	995
Asset-based Fee Revenue [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	313	327
Asset-based Fee Revenue [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	150	131
Asset-based Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	1,523	1,418
Asset-based Fee Revenue [Member] | United States [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	1,081	982
Asset-based Fee Revenue [Member] | United States [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	292	305
Asset-based Fee Revenue [Member] | United States [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	150	131
Asset-based Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	36	35
Asset-based Fee Revenue [Member] | Canada [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	15	13
Asset-based Fee Revenue [Member] | Canada [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	21	22
Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	172	172
Account and Activity Fee Revenue [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	107	109
Account and Activity Fee Revenue [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	65	63
Account and Activity Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	169	168
Account and Activity Fee Revenue [Member] | United States [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	107	109
Account and Activity Fee Revenue [Member] | United States [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	62	59
Account and Activity Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	3	4
Account and Activity Fee Revenue [Member] | Canada [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	3	4
Total Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	1,731	1,625
Total Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	1,692	1,586
Total Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	39	39
Trade Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	368	364
Trade Revenue [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	333	332
Trade Revenue [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	35	32
Trade Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	356	349
Trade Revenue [Member] | United States [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	322	318
Trade Revenue [Member] | United States [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	34	31
Trade Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	12	15
Trade Revenue [Member] | Canada [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	11	14
Trade Revenue [Member] | Canada [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	$ 1	$ 1