Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
New York City unincorporated business tax (percent)			4.00%
Federal tax rate on partnership gross income (percent)			3.50%
Computation of equity in net income attributable to AllianceBernstein Unitholders [Abstract]
Net income attributable to AB Unitholders	$ 181,665	$ 135,103	$ 365,861	$ 275,040
Multiplied by: weighted average equity ownership interest (percent)	36.00%	35.50%	35.80%	35.50%
Equity in net income attributable to AB Unitholders	$ 65,388	$ 47,947	$ 131,086	$ 97,613
Computation of income tax [Abstract]
AB qualifying revenues	$ 643,009	$ 586,478	$ 1,345,927	$ 1,132,655
Multiplied by: weighted average equity ownership interest for calculating tax (percent)	30.20%	29.70%	30.20%	29.60%
Multiplied by: federal tax (percent)	3.50%	3.50%	3.50%	3.50%
Federal income taxes	$ 6,794	$ 6,099	$ 14,204	$ 11,750
State income taxes	137	107	265	212
Total income taxes	$ 6,931	$ 6,206	$ 14,469	$ 11,962
Effective tax rate (percent)	10.60%	12.90%	11.00%	12.30%
Changes in components for calculation of income tax [Abstract]
Change in net income attributable to AllianceBernstein Unitholders (percent)	34.50%		33.00%
Change in equity in net income attributable to AllianceBernstein Unitholders (percent)	36.40%		34.30%
Change in AllianceBernstein qualifying revenues (percent)	9.60%		18.80%
Change in income taxes (percent)	11.70%		21.00%