Revenue - Receivable from Mutual Funds, Insurance Companies, and Other - Schedule of Partnership's Disaggregated Revenue (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation Of Revenue [Line Items]
Revenue	$ 12,746	$ 11,984	$ 12,143
Net interest and dividends and other revenue	1,052	285	136
Net revenue	13,798	12,269	12,279
United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	12,424	11,664	11,833
Net interest and dividends and other revenue	985	238	113
Net revenue	13,409	11,902	11,946
Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue	322	320	310
Net interest and dividends and other revenue	67	47	23
Net revenue	389	367	333
Total Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	11,264	10,500	10,424
Total Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	10,994	10,233	10,169
Total Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue	270	267	255
Asset-based Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	10,518	9,808	9,737
Asset-based Fee Revenue [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	7,814	7,384	7,421
Asset-based Fee Revenue [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,476	1,512	1,676
Asset-based Fee Revenue [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Revenue	578	280	25
Asset-based Fee Revenue [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	650	632	615
Asset-based Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	10,262	9,554	9,496
Asset-based Fee Revenue [Member] | United States [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	7,656	7,237	7,293
Asset-based Fee Revenue [Member] | United States [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,378	1,405	1,563
Asset-based Fee Revenue [Member] | United States [Member] | Cash Solutions Fees Member
Disaggregation Of Revenue [Line Items]
Revenue	578	280	25
Asset-based Fee Revenue [Member] | United States [Member] | Other Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	650	632	615
Asset-based Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue	256	254	241
Asset-based Fee Revenue [Member] | Canada [Member] | Advisory Programs Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	158	147	128
Asset-based Fee Revenue [Member] | Canada [Member] | Service Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	98	107	113
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	746	692	687
Account and Activity Fee Revenue [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	462	454	436
Account and Activity Fee Revenue [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	284	238	251
Account and Activity Fee Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	732	679	673
Account and Activity Fee Revenue [Member] | United States [Member] | Shareholder Accounting Services Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue	462	454	436
Account and Activity Fee Revenue [Member] | United States [Member] | Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	270	225	237
Account and Activity Fee Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue	14	13	14
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	13	14
Trade Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,482	1,484	1,719
Trade Revenue [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,250	1,318	1,679
Trade Revenue [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	232	166	40
Trade Revenue [Member] | United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,430	1,431	1,664
Trade Revenue [Member] | United States [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,210	1,273	1,627
Trade Revenue [Member] | United States [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	220	158	37
Trade Revenue [Member] | Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue	52	53	55
Trade Revenue [Member] | Canada [Member] | Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	40	45	52
Trade Revenue [Member] | Canada [Member] | Principal Transactions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 12	$ 8	$ 3