Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 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	$ 166,252	$ 181,665	$ 315,366	$ 365,861
Multiplied by: weighted average equity ownership interest (percent)	35.50%	36.00%	35.40%	35.80%
Equity in net income attributable to AB Unitholders	$ 59,023	$ 65,388	$ 111,661	$ 131,086
Computation of income tax [Abstract]
AB qualifying revenues	$ 643,019	$ 643,009	$ 1,229,569	$ 1,345,927
Multiplied by: weighted average equity ownership interest for calculating tax (percent)	29.40%	30.20%	29.50%	30.20%
Multiplied by: federal tax (percent)	3.50%	3.50%	3.50%	3.50%
Federal income taxes	$ 6,619	$ 6,794	$ 12,700	$ 14,204
State income taxes	130	137	248	265
Total income taxes	$ 6,749	$ 6,931	$ 12,948	$ 14,469
Effective tax rate (percent)	11.40%	10.60%	11.60%	11.00%
Changes in components for calculation of income tax [Abstract]
Change in net income attributable to AllianceBernstein Unitholders (percent)	(8.50%)		(13.80%)
Change in equity in net income attributable to AllianceBernstein Unitholders (percent)	(9.70%)		(14.80%)
Change in AllianceBernstein qualifying revenues (percent)	0.00%		(8.60%)
Change in income taxes (percent)	(2.60%)		(10.50%)