Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 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	$ 149,114	$ 184,196
Multiplied by: weighted average equity ownership interest (percent)	35.30%	35.70%
Equity in net income attributable to AB Unitholders	$ 52,638	$ 65,698
Computation of income tax [Abstract]
AB qualifying revenues	$ 586,550	$ 702,919
Multiplied by: weighted average equity ownership interest for calculating tax (percent)	29.60%	30.10%
Multiplied by: federal tax (percent)	3.50%	3.50%
Federal income taxes	$ 6,081	$ 7,410
State income taxes	118	128
Total income taxes	$ 6,199	$ 7,538
Effective tax rate (percent)	11.80%	11.50%
Changes in components for calculation of income tax [Abstract]
Change in net income attributable to AllianceBernstein Unitholders (percent)	(19.00%)
Change in equity in net income attributable to AllianceBernstein Unitholders (percent)	(19.90%)
Change in AllianceBernstein qualifying revenues (percent)	(16.60%)
Change in income taxes (percent)	(17.80%)