Receivables and Revenue - Schedule of Partnership's Disaggregated Revenue (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 25, 2021	Jun. 26, 2020	Jun. 25, 2021	Jun. 26, 2020
Disaggregation Of Revenue [Line Items]
Net revenue	$ 2,993	$ 2,273	$ 5,814	$ 4,743
Net interest and dividends and other revenue	41	52	73	73
Net revenue	3,034	2,325	5,887	4,816
United States [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	2,915	2,216	5,666	4,626
Net interest and dividends and other revenue	39	45	67	58
Net revenue	2,954	2,261	5,733	4,684
Canada [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	78	57	148	117
Net interest and dividends and other revenue	2	7	6	15
Net revenue	80	64	154	132
Asset-based Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	2,385	1,718	4,594	3,524
Asset-based Fee Revenue [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	1,813	1,258	3,480	2,558
Asset-based Fee Revenue [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	417	323	808	663
Asset-based Fee Revenue [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	155	137	306	303
Asset-based Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	2,325	1,679	4,482	3,442
Asset-based Fee Revenue [Member] | United States [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	1,782	1,238	3,422	2,519
Asset-based Fee Revenue [Member] | United States [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	388	304	754	620
Asset-based Fee Revenue [Member] | United States [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	155	137	306	303
Asset-based Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	60	39	112	82
Asset-based Fee Revenue [Member] | Canada [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	31	20	58	39
Asset-based Fee Revenue [Member] | Canada [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	29	19	54	43
Asset-based Fee Revenue [Member] | Canada [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	0	0	0	0
Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	171	160	341	331
Account and Activity Fee Revenue [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	109	104	216	213
Account and Activity Fee Revenue [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	62	56	125	118
Account and Activity Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	168	157	334	325
Account and Activity Fee Revenue [Member] | United States [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	109	104	216	213
Account and Activity Fee Revenue [Member] | United States [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	59	53	118	112
Account and Activity Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	3	3	7	6
Account and Activity Fee Revenue [Member] | Canada [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	0	0	0	0
Account and Activity Fee Revenue [Member] | Canada [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	3	3	7	6
Total Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	2,556	1,878	4,935	3,855
Total Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	2,493	1,836	4,816	3,767
Total Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	63	42	119	88
Trade Revenue [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	437	395	879	888
Trade Revenue [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	426	378	859	855
Trade Revenue [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	11	17	20	33
Trade Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	422	380	850	859
Trade Revenue [Member] | United States [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	412	364	831	828
Trade Revenue [Member] | United States [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	10	16	19	31
Trade Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	15	15	29	29
Trade Revenue [Member] | Canada [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	14	14	28	27
Trade Revenue [Member] | Canada [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Net revenue	$ 1	$ 1	$ 1	$ 2