Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2024 USD ($) CapitalRepayment Segment CapitalClass	Dec. 31, 2023 USD ($) Segment	Dec. 31, 2022 USD ($) Segment	Feb. 28, 2025 USD ($)	Jan. 01, 2025 USD ($)	Jan. 01, 2024 USD ($)
Basis Of Presentation [Line Items]
Number of operating segments | Segment	2	2	2
Period for partner's capital redemption in the event of death	6 months
Number of annual capital repayments for withdrawal of limited partners | Segment	3
Period to begin repaying capital upon withdrawal for limited partners	90 days
Number of annual capital repayments for withdrawal of subordinated limited partners | CapitalRepayment	6
Period to begin repaying capital upon withdrawal for subordinated limited partners	90 days
Fair value of level III, assets	$ 0	$ 0
Fair value of level III, liabilities	0	0
Compensation expense	0
Notional capital granted and issued				$ 440,465,500	$ 196,000,000	$ 263,000,000
Notional capital forfeited	3,000,000
Notional capital expired	15,000,000
Liability for the future payments due to financial advisors	$ 277,000,000
Retirement and transition employment agreement term	5 years
Retirement transition plan employment term	2 years
Retirement transition plan non-compete term	3 years
Retirement transition plan compensation paid term	4 years
Retirement transition plan accrued future payments	$ 228,000,000	150,000,000
Retirement transition plan accrued future payments expected to be paid in 2024	98,000,000
Net Income (Loss)	$ 0	$ 0	$ 0
Number of classes of capital | CapitalClass	3
Limited partnership's minimum annual return rate	7.50%	7.50%	7.50%
Collateral held for margin loans	$ 5,119,000,000	$ 4,231,000,000
Stock based compensation, description	The Profits Interests are fully vested and participate in Net Income allocations upon grant. Any future rights to allocations and distributions of the Partnership's Net Income will be forfeited upon termination of the Profits Interests. Profits Interests have zero fair value on the grant date, therefore no compensation expense is recognized upon issuance or over their stated term. During 2024, $3 of Notional Capital was forfeited and $15 of Notional Capital expired.
Maximum Percentage Of Margin Loan Balance Compared To Value Of Collateral Securities In Accordance With Partnerships Policy	65.00%
Partners [Member]
Basis Of Presentation [Line Items]
Expected credit loss	$ 0	0
Other Customer [Member]
Basis Of Presentation [Line Items]
Expected credit loss	0	0
Securities Purchase Agreement [Member]
Basis Of Presentation [Line Items]
Fair value of collateral related to resell agreements	1,414,000,000	1,158,000,000
Expected credit loss	$ 0	0
Building [Member]
Basis Of Presentation [Line Items]
Equipment, property and improvements estimated useful lives	30 years
Lessee Operating Branch Office Spaces [Member]
Basis Of Presentation [Line Items]
Lessee, operating lease, description	The Partnership leases branch office space under numerous operating leases from non-affiliates and to a lesser extent, financial advisors or their affiliates. Branch offices are generally leased for terms of five years and generally contain a renewal option.
Lessee, operating lease term of contract	5 years
Lessee Operating Lease Home Office Spaces [Member]
Basis Of Presentation [Line Items]
Lessee, operating lease, description	The Partnership also leases a home office space and land from non-affiliates with terms ranging from 12 to 30 years.
Customer Receivables [Member]
Basis Of Presentation [Line Items]
Expected credit loss	$ 0	$ 0
Minimum [Member]
Basis Of Presentation [Line Items]
Retirement transition plan compensation expense term	1 year
Lessee, operating lease term of contract	12 years
Term of receivables from revenue from contracts with customers	30 days
Minimum [Member] | United States [Member] | Securities Purchase Agreement [Member]
Basis Of Presentation [Line Items]
Fair value of underlying collateral as percentage of carrying value of transaction	102.00%
Minimum [Member] | Canada [Member] | Securities Purchase Agreement [Member]
Basis Of Presentation [Line Items]
Fair value of underlying collateral as percentage of carrying value of transaction	100.00%
Minimum [Member] | Equipment [Member]
Basis Of Presentation [Line Items]
Equipment, property and improvements estimated useful lives	3 years
Maximum [Member]
Basis Of Presentation [Line Items]
Retirement transition plan compensation expense term	2 years
Lessee, operating lease term of contract	30 years
Term of receivables from revenue from contracts with customers	90 days
Maximum [Member] | Equipment [Member]
Basis Of Presentation [Line Items]
Equipment, property and improvements estimated useful lives	7 years