Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
New York City unincorporated business tax (percent)			4.00%
Federal tax rate on partnership gross income (percent)			3.50%
Income Tax Contingency [Line Items]
Multiplied by: weighted average equity ownership interest (percent)	35.60%	35.50%	35.80%	35.40%
Equity in net income attributable to AB Unitholders	$ 63,201	$ 59,023	$ 133,115	$ 111,661
Computation of income tax [Abstract]
AB qualifying revenues	$ 586,609	$ 643,019	$ 1,288,949	$ 1,229,569
Multiplied by: weighted average equity ownership interest for calculating tax (percent)	29.90%	29.40%	30.40%	29.50%
Multiplied by: federal tax (percent)	3.50%	3.50%	3.50%	3.50%
Federal income taxes	$ 6,179	$ 6,619	$ 13,694	$ 12,700
State income taxes	96	130	236	248
Total income taxes	$ 6,275	$ 6,749	$ 13,930	$ 12,948
Effective tax rate (percent)	9.90%	11.40%	10.50%	11.60%
Changes in components for calculation of income tax [Abstract]
Change in net income attributable to AllianceBernstein Unitholders (percent)	6.70%		17.80%
Change in equity in net income attributable to AllianceBernstein Unitholders (percent)	7.10%		19.20%
Change in AllianceBernstein qualifying revenues (percent)	(8.80%)		4.80%
Change in income taxes (percent)	(7.00%)		7.60%
Variable Interest Entity, Primary Beneficiary
Income Tax Contingency [Line Items]
Net income attributable to AB Unitholders	$ 177,321	$ 166,252	$ 371,641	$ 315,366