Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Taxes [Abstract]
New York City unincorporated business tax (in hundredths)			4.00%
Computation of equity in net income attributable to AllianceBernstein Unitholders [Abstract]
Net income attributable to AllianceBernstein Unitholders	$ 139,798	$ 99,948	$ 392,958	$ 335,178
Multiplied by: weighted average equity ownership interest (in hundredths)	35.70%	34.50%	35.60%	36.70%
Equity in net income attributable to AllianceBernstein Unitholders	49,876	34,504	139,714	122,941
Computation of income tax [Abstract]
AllianceBernstein qualifying revenues	548,319	502,423	1,581,456	1,496,177
Multiplied by: weighted average equity ownership interest for calculating tax (in hundredths)	29.40%	27.90%	29.40%	27.90%
Multiplied by: federal tax (in hundredths)	3.50%	3.50%	3.50%	3.50%
Federal income taxes	5,642	4,901	16,267	14,631
State income taxes	100	80	300	280
Total income taxes	$ 5,742	$ 4,981	$ 16,567	$ 14,911
Effective tax rate (in hundredths)	11.50%	14.40%	11.90%	12.10%
Changes in components for calculation of income tax [Abstract]
Increase in net income attributable to AllianceBernstein Unitholders (in hundredths)	39.90%		17.20%
Increase in equity in net income attributable to AllianceBernstein Unitholders (in hundredths)	44.60%		13.60%
Change in AllianceBernstein qualifying revenues (in hundredths)	9.10%		5.70%
Increase in income taxes (in hundredths)	15.30%		11.10%