Basis of presentation.

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Number of annual capital repayments to limited partners withdrawing from the partnership.

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Minimum period to receive distribution by subordinated limited partners.

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Number of classes of capital in the partnership.

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Partnership agreement partners capital redemption period.

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Reduction in right-of-use asset for deferred rent on existing leases at adoption.

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Retirement transition employment agreement term.

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Retirement transition plan accrued future payments expected to be paid.

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Term for compensation expense recognition under the retirement transition plan.

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Term for compensation paid under the retirement transition plan, which is made ratably over the period.

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Term as employee under the retirement transition plan.

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Term for non-compete agreement under the retirement transition plan.

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Securities purchased under agreements to resell fair value of underlying collateral percentage.

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Assets categorized as level III during the reporting period.

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Liabilities categorized as level III during the reporting period.

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Fair value of collateral permitted, by contact or custom, to be sold or re-pledged.

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Description of lessee's operating lease.

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Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Present value of lessee's discounted obligation for lease payments from operating lease.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) Segment Capital_Repayment CapitalClass	Dec. 31, 2018 USD ($) Segment	Dec. 31, 2017 USD ($) Segment	Jan. 01, 2019 USD ($)
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 \| Capital_Repayment	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
Fair value of collateral related to resell agreements	$ 1,724,000,000	926,000,000
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	$ 102,000,000	94,000,000
Retirement transition plan accrued future payments expected to be paid in 2020	52,000,000
Net income	$ 0	$ 0	$ 0
Number of classes of capital \| CapitalClass	3
Limited partnership's minimum annual return rate	7.50%	7.50%	7.50%
Lease right-of-use asset	$ 876,000,000	$ 0
Lease liability	$ 898,000,000	$ 0
ASC 842 [Member]
Basis Of Presentation [Line Items]
Lease right-of-use asset				$ 785,000,000
Lease liability				805,000,000
Reduction in right-of-use asset for deferred rent				20,000,000
Cumulative-effect adjustment to the opening balance of Partnership capital				$ 0
Building [Member]
Basis Of Presentation [Line Items]
Equipment, property and improvements estimated useful lives	30 years
Branch Office Space [Member]
Basis Of Presentation [Line Items]
Lessee, operating lease, description	The Partnership leases branch office space under numerous operating leases from non-affiliates and financial advisors. 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 home office spaces and land from non-affiliates with terms ranging from 12 to 30 years.
United States [Member]
Basis Of Presentation [Line Items]
Fair value of underlying collateral as percentage of carrying value of transaction	102.00%	102.00%
Canada [Member]
Basis Of Presentation [Line Items]
Fair value of underlying collateral as percentage of carrying value of transaction	100.00%	100.00%
Minimum [Member]
Basis Of Presentation [Line Items]
Retirement transition plan compensation expense term	1 year
Minimum [Member] \| Equipment [Member]
Basis Of Presentation [Line Items]
Equipment, property and improvements estimated useful lives	3 years
Minimum [Member] \| Lessee Operating Lease Home Office Spaces [Member]
Basis Of Presentation [Line Items]
Lessee, operating lease term of contract	12 years
Maximum [Member]
Basis Of Presentation [Line Items]
Retirement transition plan compensation expense term	2 years
Retirement transition plan compensation on transitioned assets term	4 years
Maximum [Member] \| Equipment [Member]
Basis Of Presentation [Line Items]
Equipment, property and improvements estimated useful lives	10 years
Maximum [Member] \| Lessee Operating Lease Home Office Spaces [Member]
Basis Of Presentation [Line Items]
Lessee, operating lease term of contract	30 years
Securities Purchase Agreement [Member] \| Minimum [Member] \| United States [Member]
Basis Of Presentation [Line Items]
Fair value of underlying collateral as percentage of carrying value of transaction	102.00%
Securities Purchase Agreement [Member] \| Minimum [Member] \| Canada [Member]
Basis Of Presentation [Line Items]
Fair value of underlying collateral as percentage of carrying value of transaction	100.00%