Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
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	$ 187,811	$ 203,674	$ 503,177	$ 569,535
Multiplied by: weighted average equity ownership interest (percent)	35.50%	35.70%	35.50%	35.80%
Equity in net income attributable to AB Unitholders	$ 66,722	$ 72,802	$ 178,383	$ 203,888
Computation of income tax [Abstract]
AB qualifying revenues	$ 656,173	$ 649,270	$ 1,886,176	$ 1,995,197
Multiplied by: weighted average equity ownership interest for calculating tax (percent)	29.40%	29.80%	29.50%	30.00%
Multiplied by: federal tax (percent)	3.50%	3.50%	3.50%	3.50%
Federal income taxes	$ 6,759	$ 6,775	$ 19,459	$ 20,979
State income taxes	135	127	383	392
Total income taxes	$ 6,894	$ 6,902	$ 19,842	$ 21,371
Effective tax rate (percent)	10.30%	9.50%	11.10%	10.50%
Changes in components for calculation of income tax [Abstract]
Change in net income attributable to AllianceBernstein Unitholders (percent)	(7.80%)		(11.70%)
Change in equity in net income attributable to AllianceBernstein Unitholders (percent)	(8.40%)		(12.50%)
Change in AllianceBernstein qualifying revenues (percent)	1.10%		(5.50%)
Change in income taxes (percent)	(0.10%)		(7.20%)