Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
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	$ 194,320	$ 149,114
Multiplied by: weighted average equity ownership interest (percent)	36.00%	35.30%
Equity in net income attributable to AB Unitholders	$ 69,914	$ 52,638
Computation of income tax [Abstract]
AB qualifying revenues	$ 702,340	$ 586,550
Multiplied by: weighted average equity ownership interest for calculating tax (percent)	30.60%	29.60%
Multiplied by: federal tax (percent)	3.50%	3.50%
Federal income taxes	$ 7,515	$ 6,081
State income taxes	140	118
Total income taxes	$ 7,655	$ 6,199
Effective tax rate (percent)	10.90%	11.80%
Changes in components for calculation of income tax [Abstract]
Change in net income attributable to AllianceBernstein Unitholders (percent)	30.30%
Change in equity in net income attributable to AllianceBernstein Unitholders (percent)	32.80%
Change in AllianceBernstein qualifying revenues (percent)	19.70%
Change in income taxes (percent)	23.50%