Revenue - Schedule of Partnership's Disaggregated Revenue (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation Of Revenue [Line Items]
Revenue	$ 14,923	$ 12,746	$ 11,984
Net interest and dividends and other revenue	1,081	1,052	285
Net revenue	16,004	13,798	12,269
United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	14,555	12,424	11,664
Net interest and dividends and other revenue	1,006	985	238
Net revenue	15,561	13,409	11,902
Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue	368	322	320
Net interest and dividends and other revenue	75	67	47
Net revenue	443	389	367
Total Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	13,163	11,264	10,500
Total Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	12,856	10,994	10,233
Total Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue	307	270	267
Asset-based Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	12,408	10,518	9,808
Asset-based Fee Revenue [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	9,463	7,814	7,384
Asset-based Fee Revenue [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,627	1,476	1,512
Asset-based Fee Revenue [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Revenue	580	578	280
Asset-based Fee Revenue [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	738	650	632
Asset-based Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	12,115	10,262	9,554
Asset-based Fee Revenue [Member] | United States [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	9,274	7,656	7,237
Asset-based Fee Revenue [Member] | United States [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,523	1,378	1,405
Asset-based Fee Revenue [Member] | United States [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Revenue	580	578	280
Asset-based Fee Revenue [Member] | United States [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	738	650	632
Asset-based Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue	293	256	254
Asset-based Fee Revenue [Member] | Canada [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	189	158	147
Asset-based Fee Revenue [Member] | Canada [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	104	98	107
Asset-based Fee Revenue [Member] | Canada [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Revenue	0	0	0
Asset-based Fee Revenue [Member] | Canada [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	0	0	0
Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	755	746	692
Account and Activity Fee Revenue [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	466	462	454
Account and Activity Fee Revenue [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	289	284	238
Account and Activity Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	741	732	679
Account and Activity Fee Revenue [Member] | United States [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	466	462	454
Account and Activity Fee Revenue [Member] | United States [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	275	270	225
Account and Activity Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue	14	14	13
Account and Activity Fee Revenue [Member] | Canada [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	0	0	0
Account and Activity Fee Revenue [Member] | Canada [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	14	14	13
Trade Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,760	1,482	1,484
Trade Revenue [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,533	1,250	1,318
Trade Revenue [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	227	232	166
Trade Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,699	1,430	1,431
Trade Revenue [Member] | United States [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,483	1,210	1,273
Trade Revenue [Member] | United States [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	216	220	158
Trade Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue	61	52	53
Trade Revenue [Member] | Canada [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	50	40	45
Trade Revenue [Member] | Canada [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 11	$ 12	$ 8