Summary of Significant Accounting Policies (Details)			1 Months Ended		3 Months Ended								12 Months Ended
		Feb. 11, 2016 $ / shares	Dec. 31, 2015 USD ($) Entity shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2015 USD ($) Entity $ / shares	Sep. 30, 2015 $ / shares	Jun. 30, 2015 $ / shares	Mar. 31, 2015 $ / shares	Dec. 31, 2014 USD ($) $ / shares	Sep. 30, 2014 $ / shares	Jun. 30, 2014 $ / shares	Mar. 31, 2014 $ / shares	Dec. 31, 2015 USD ($) investment Entity shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)
Variable Interest Entities [Abstract]
Weighted average age of seed investment portfolio													17 months
Percentage of annual turn over on seed investments, percent													50.00%
Large seed capital investments, minimum			$ 1,000,000		$ 1,000,000								$ 1,000,000
Large seed capital investments, maximum			35,000,000		35,000,000								35,000,000
Large seed capital investments, average			10,000,000		10,000,000								10,000,000
Ceiling established by Audit Committee of Board of Directors for seed investment program			$ 650,000,000		$ 650,000,000								$ 650,000,000
Number of collateralized debt obligations managed that meet the definition of a Variable Interest Entities due primarily to the lack of unilateral decision-making authority of the equity holders | Entity			1		1								1
Cash of the variable interest entity			$ 9,400,000		$ 9,400,000								$ 9,400,000
Collateral investments (at fair value) of the variable interest entity			52,300,000		52,300,000								52,300,000
Notes payable (at amortized cost) of the variable interest entity			53,400,000		53,400,000								53,400,000
Variable interests in certain structured products and hedge funds			28,300,000		28,300,000								28,300,000
Our maximum exposure to loss is limited to our investment in these entities			200,000		200,000								200,000
Collateralized Securities Transactions [Abstract]
Securities held as collateral for receivables & re-pledged			500,000		500,000								500,000
Cash on deposit with clearing organizations for trade facilitation purposes			81,400,000	$ 26,300,000	81,400,000				$ 26,300,000				81,400,000	$ 26,300,000
SCB LLC held U.S. Treasury Bills			$ 24,900,000	$ 29,000,000	$ 24,900,000				$ 29,000,000				$ 24,900,000	$ 29,000,000
Schedule of Equity Method Investments [Line Items]
Private equity investments owned outside of consolidated venture capital fund | investment													3
Private equity investments owned outside consolidated venture capital fund accounted for using cost method | investment													1
Private equity investments owned outside consolidated venture capital fund accounted for fair value | investment													2
Deferred Sales Commissions, Net [Abstract]
Period of time the deferred sales commissions are amortized over for U.S. fund shares													5 years 6 months
Period of time the deferred sales commissions are amortized over for non-U.S. fund shares													4 years
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 awards vesting periods													4 years
Long-term incentive cash maximum per employee			$ 250,000		$ 250,000								$ 250,000
Period over which holding units are typically distributed to Directors													3 years
AB Holding Units purchased in periods (in units) | shares													8,500,000	3,600,000
Dollar amount paid for AB Holding Units acquired													$ 218,300,000	$ 92,800,000
Open-market purchases of AB Holding Units (in units) | shares													5,800,000	300,000
Dollar amount paid for open-market purchases of AB Holding Units													$ 151,100,000	$ 7,200,000
Restricted AB Holding Units awarded to employees (in units) | shares			7,000,000	6,600,000									7,400,000	7,600,000
Units issued upon exercise of options (in units) | shares													541,073	1,110,070
Proceeds from stock options exercised													$ 9,233,000	$ 18,955,000	$ 15,138,000
Foreign Currency Translations [Abstract]
Net foreign currency transaction gains (losses)													$ 1,000,000	$ (1,600,000)	$ (3,100,000)
Cash Distribution [Line Items]
Percentage of General Partnership interest in company													1.00%
Cash distribution, distribution declared (in dollars per unit) | $ / shares	[1],[2]				$ 0.56	$ 0.50	$ 0.54	$ 0.51	$ 0.63	$ 0.51	$ 0.50	$ 0.44
Cash Distribution [Member]
Cash Distribution [Line Items]
Cash distribution, declaration date													Feb. 11, 2016
Percentage of General Partnership interest in company													1.00%
Cash distribution, distribution date													Mar. 10, 2016
Cash distribution, date of record													Feb. 22, 2016
Employees Based Outside of the United States [Member]
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
Subsequent Event [Member] | Cash Distribution [Member]
Cash Distribution [Line Items]
Cash distribution, distribution declared (in dollars per unit) | $ / shares		$ 0.56
Furniture [Member]
Furniture, Equipment and Leasehold Improvements [Abstract]
Useful Life													8 years
Equipment [Member] | Minimum [Member]
Furniture, Equipment and Leasehold Improvements [Abstract]
Useful Life													3 years
Equipment [Member] | Maximum [Member]
Furniture, Equipment and Leasehold Improvements [Abstract]
Useful Life													6 years
Consolidated Private Equity Fund [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage			10.00%		10.00%								10.00%

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

[2] Declared and paid during the following quarter.