Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)			1 Months Ended	3 Months Ended								12 Months Ended
		Feb. 11, 2021	Dec. 31, 2020	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Collateralized Securities Transactions [Abstract]
Repledged securities			$ 0	$ 0								$ 0
Collateral advances, allowance			0	0				$ 0				0	$ 0
Cash on deposit with clearing organizations for trade facilitation purposes			130,000,000.0	130,000,000.0				204,000,000.0				130,000,000.0	204,000,000.0
SCB LLC held U.S. Treasury Bills			$ 0	$ 0				$ 0				$ 0	0
Deferred Sales Commissions, Net [Abstract]
Period of time the deferred sales commissions are amortized over for U.S. fund shares												1 year
Period of time the deferred sales commissions are amortized over for non-U.S. fund shares												4 years
Impairment of finite-lived intangible assets												$ 0	0
Business Acquisition [Line Items]
Contingent payment arrangements												$ 1,855,000	$ (510,000)	$ (2,219,000)
Mutual Fund Underwriting Activities [Abstract]
Period over which receivables from brokers and dealers for sale of shares of company-sponsored mutual funds generally are realized												3 days
Long-term Incentive Compensation Plans [Abstract]
Employee allocation percentage maximum, percent			50.00%	50.00%								50.00%
Long-term incentive cash maximum per employee			$ 250,000	$ 250,000								$ 250,000
Long-term incentive awards vesting periods												4 years
AB Holding Units purchased in periods (in units)												5,400,000	6,000,000.0
Dollar amount paid for AB Holding Units acquired												$ 149,000,000.0	$ 172,600,000
Open-market purchases of AB Holding Units (in units)												3,100,000	2,900,000
Dollar amount paid for open-market purchases of AB holding units												$ 74,000,000.0	$ 82,700,000
Restricted AB Holding Units awarded to employees (in units)			5,000,000.0									5,700,000	7,700,000	5,400,000
Units issued upon exercise of options (in units)												5,182	511,894
Proceeds from stock options exercised												$ 147,000	$ 11,511,000	$ 16,589,000
Foreign Currency Translations [Abstract]
Net foreign currency transaction gains (losses)												$ (3,300,000)	$ (2,000,000.0)	$ (100,000)
Cash Distribution [Line Items]
Cash distribution, distribution declared (in dollars per unit)	[1],[2]			$ 1.05	$ 0.76	$ 0.68	$ 0.71	$ 0.93	$ 0.70	$ 0.63	$ 0.56
Cash distributions per unit paid to the General Partner and Unitholders (in dollars per unit)												$ 3.08	$ 2.60	$ 3.16
Subsequent Event | Cash Distribution
Cash Distribution [Line Items]
Cash distribution, distribution declared (in dollars per unit)		$ 1.05
Employees based outside of the United States
Long-term Incentive Compensation Plans [Abstract]
Employee allocation percentage maximum, percent			100.00%	100.00%								100.00%
Long-term incentive cash maximum per employee			$ 100,000	$ 100,000								$ 100,000
Furniture
Furniture, Equipment and Leasehold Improvements [Abstract]
Useful Life												8 years
Equipment | Minimum
Furniture, Equipment and Leasehold Improvements [Abstract]
Useful Life												3 years
Equipment | Maximum
Furniture, Equipment and Leasehold Improvements [Abstract]
Useful Life												6 years
AllianceBernstein Corporation | AB Holding
Cash Distribution [Line Items]
Percentage of General Partnership interest in company												1.00%
Ramius Alternative Solutions LLC
Business Acquisition [Line Items]
Contingent payment arrangements				$ 1,400,000

[1] Cash distributions reflect the impact of our non-GAAP adjustments.

[2] Declared and paid during the following quarter.