Summary of Significant Accounting Policies - Additional Information (Details) $ / shares in Units, shares in Millions		1 Months Ended		3 Months Ended				12 Months Ended
	Feb. 06, 2025 $ / shares	Dec. 31, 2024 USD ($) investment shares	Dec. 31, 2023 USD ($) investment shares	Dec. 31, 2024 USD ($) investment	Dec. 31, 2023 USD ($) investment	Dec. 31, 2022 USD ($)	Sep. 30, 2022	Dec. 31, 2024 USD ($) investment $ / shares shares	Dec. 31, 2023 USD ($) investment $ / shares shares	Dec. 31, 2022 USD ($) $ / shares	Nov. 30, 2024	Apr. 01, 2024 USD ($) jointVenture
Business Acquisition [Line Items]
Investments owned		$ 535,204,000	$ 243,554,000	$ 535,204,000	$ 243,554,000			$ 535,204,000	$ 243,554,000
Joint ventures		286,721,000	0	286,721,000	0			286,721,000	0
Repledged securities		0	122,400,000	0	122,400,000			0	122,400,000
Collateral advances, allowance		0	0	0	0			0	0
Cash on deposit with clearing organization		29,100,000	10,200,000	29,100,000	10,200,000			29,100,000	10,200,000
U.S. Treasury bills pledged as collateral		0	0	0	0			0	0
Goodwill		3,598,591,000	3,598,591,000	3,598,591,000	3,598,591,000			3,598,591,000	3,598,591,000
Impairment of finite-lived intangible assets				0	0				0	$ 5,600,000
Contingent consideration liability		9,385,000	252,690,000	9,385,000	252,690,000			9,385,000	252,690,000
Increase (decrease) in contingent consideration payable								(130,901,000)	14,050,000	0
Accounts payable and accrued expenses		426,675,000	172,163,000	426,675,000	172,163,000			426,675,000	172,163,000
Business combination, contingent consideration arrangements, change in amount of contingent consideration, liability impairments									0	0
Intangible assets, net of accumulated amortization		215,054,000	264,555,000	215,054,000	264,555,000			215,054,000	264,555,000
Finite-lived intangible assets subject to amortization, net		199,800,000	249,400,000	199,800,000	249,400,000			199,800,000	249,400,000
Indefinite-lived intangible assets not subject to amortization		15,300,000	15,200,000	15,300,000	15,200,000			15,300,000	15,200,000
Finite-lived intangible assets		320,800,000	328,400,000	320,800,000	328,400,000			320,800,000	328,400,000
Accumulated amortization of intangible assets		121,000,000.0	79,000,000.0	121,000,000.0	$ 79,000,000.0			121,000,000.0	79,000,000.0
Amortization of intangible assets								45,913,000	46,854,000	$ 26,564,000
2026		45,000,000		45,000,000				45,000,000
2024		45,000,000		45,000,000				45,000,000
2025		45,000,000		45,000,000				45,000,000
2027		24,000,000		24,000,000				24,000,000
2028		24,000,000		$ 24,000,000				$ 24,000,000
Impairment, Intangible Asset, Finite-Lived, Statement of Income or Comprehensive Income [Extensible Enumeration]				General and administrative	General and administrative	General and administrative
Deferred sales commission amortization period US fund (in years)								1 year
Deferred sales commission amortization period non US funds (in years)								4 years
Assets held for sale		0	564,776,000	$ 0	$ 564,776,000			$ 0	564,776,000
Liabilities held for sale		$ 0	$ 153,342,000	$ 0	$ 153,342,000			$ 0	$ 153,342,000
Period over which receivables from brokers and dealers for sale of shares of company-sponsored mutual funds generally are realized								3 days
Maximum percentage of award an employee can elect to allocate to deferred cash		50.00%	50.00%	50.00%	50.00%	50.00%		50.00%	50.00%	50.00%
Maximum amount of deferred cash		$ 250,000	$ 250,000	$ 250,000	$ 250,000	$ 250,000		$ 250,000	$ 250,000	$ 250,000
Granted to employees and eligible directors | shares		4.1	5.0					5.9	5.6
Net foreign currency transaction gains (losses)								$ 3,700,000	$ 4,500,000	$ 10,200,000
Cash distributions per unit paid to the general partner and unitholders (in dollars per unit) | $ / shares								$ 3.30	$ 2.92	$ 3.87
Bernstein Research Services
Business Acquisition [Line Items]
Held for sale asset disposal group		$ 159,800,000		159,800,000				$ 159,800,000
Subsequent Event
Business Acquisition [Line Items]
Cash distribution, distribution declared (in dollars per unit) | $ / shares	$ 1.15
Director
Business Acquisition [Line Items]
Long-term incentive awards vesting periods								3 years
Employees based outside of the United States
Business Acquisition [Line Items]
Maximum percentage of award an employee can elect to allocate to deferred cash			100.00%		100.00%	100.00%			100.00%	100.00%	100.00%
Maximum amount of deferred cash		$ 100,000	$ 100,000	$ 100,000	$ 100,000	$ 100,000		$ 100,000	$ 100,000	$ 100,000
Employees based outside of the United States | Long-term Incentive Compensation Plan, Deferral Limit
Business Acquisition [Line Items]
Maximum percentage of award an employee can elect to allocate to deferred cash		50.00%		50.00%				50.00%
Maximum amount of deferred cash			500,000		500,000				500,000
Employees based outside of the United States | Long-term Incentive Compensation Plan, Awards Below Deferral Limit
Business Acquisition [Line Items]
Maximum percentage of award an employee can elect to allocate to deferred cash		100.00%		100.00%				100.00%
Maximum amount of deferred cash		$ 500,000		$ 500,000				$ 500,000
Deferred Sales Commissions
Business Acquisition [Line Items]
Impairment of finite-lived intangible assets								0	0
CarVal
Business Acquisition [Line Items]
Goodwill		666,100,000		666,100,000				666,100,000
Contingent consideration liability			$ 238,500,000		$ 238,500,000				$ 238,500,000
Business combination, contingent consideration, performance term							6 years			6 years
Increase (decrease) in contingent consideration payable								(128,500,000)
Amount of settlement		134,000,000		134,000,000				134,000,000
Accounts payable and accrued expenses		118,800,000		118,800,000				118,800,000
Sanford C Bernstein Inc Acquisition
Business Acquisition [Line Items]
Goodwill		2,600,000,000		2,600,000,000				2,600,000,000
Various smaller acquisitions
Business Acquisition [Line Items]
Goodwill		291,900,000		291,900,000				291,900,000
Ramius Alternative Solutions LLC
Business Acquisition [Line Items]
Impairment of finite-lived intangible assets						4,400,000
Anchorpath
Business Acquisition [Line Items]
Impairment charge								2,500,000
Autonomous LLC
Business Acquisition [Line Items]
Transaction costs		28,400,000		28,400,000				28,400,000
Autonomous LLC | Contingent Payment Arrangement Expense
Business Acquisition [Line Items]
Transaction costs		14,100,000		14,100,000				14,100,000
Autonomous LLC | Compensation and Benefits Expense
Business Acquisition [Line Items]
Transaction costs		$ 14,300,000		$ 14,300,000				$ 14,300,000
CPH Capital
Business Acquisition [Line Items]
Impairment of finite-lived intangible assets						5,600,000
Minimum
Business Acquisition [Line Items]
Intangible assets acquired, estimated useful life		5 years		5 years				5 years
Minimum | Employee
Business Acquisition [Line Items]
Long-term incentive awards vesting periods								3 years
Minimum | CarVal
Business Acquisition [Line Items]
Contingent consideration liability						0				$ 0
Maximum
Business Acquisition [Line Items]
Intangible assets acquired, estimated useful life		20 years		20 years				20 years
Maximum | Employee
Business Acquisition [Line Items]
Long-term incentive awards vesting periods								4 years
Maximum | CarVal
Business Acquisition [Line Items]
Contingent consideration liability						$ 650,000,000				$ 650,000,000
Furniture
Business Acquisition [Line Items]
Useful life (in years)		8 years		8 years				8 years
Equipment | Minimum
Business Acquisition [Line Items]
Useful life (in years)		3 years		3 years				3 years
Equipment | Maximum
Business Acquisition [Line Items]
Useful life (in years)		6 years		6 years				6 years
AB | AB Holding
Business Acquisition [Line Items]
General partnership interest in company (percent)								1.00%
Joint Venture
Business Acquisition [Line Items]
Number of joint venture entities		2	2	2	2			2	2			2
Investments owned												$ 283,900,000
Joint ventures		$ 286,700,000		$ 286,700,000				$ 286,700,000
Joint Venture, North America
Business Acquisition [Line Items]
Interest in the joint venture		66.70%		66.70%				66.70%				66.70%
Joint Venture, International
Business Acquisition [Line Items]
Interest in the joint venture		49.00%		49.00%				49.00%