Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
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 (loss) income attributable to AllianceBernstein Unitholders	$ (44,246)		$ 90,981		$ 117,217		$ 341,592
Multiplied by: weighted average equity ownership interest (in hundredths)	37.50%	[1]	37.50%	[1]	37.50%	[1]	37.40%	[1]
Equity in net (loss) income attributable to AllianceBernstein Unitholders	(16,595)		34,074		43,915		127,877
Computation of income tax [Abstract]
AllianceBernstein qualifying revenues	492,996		533,542		1,428,600		1,633,584
Multiplied by: weighted average equity ownership interest (in hundredths)	37.50%	[1]	37.50%	[1]	37.50%	[1]	37.40%	[1]
Multiplied by: federal tax (in hundredths)	3.50%		3.50%		3.50%		3.50%
Income taxes	$ 6,547		$ 7,071		$ 19,019		$ 21,682
Effective tax rate (in hundredths)	39.50%		20.80%		43.30%		17.00%
Changes in components for calculation of income tax [Abstract]
Decrease in net income attributable to AllianceBernstein Unitholders (in hundredths)					(65.70%)
Decrease in equity in net income attributable to AllianceBernstein Unitholders (in hundredths)					(65.70%)
Decrease in AllianceBernstein qualifying revenue (in hundredths)	(7.60%)				(12.50%)
Decrease in income taxes (in hundredths)	(7.40%)				(12.30%)

[1] Equity in net (loss) income attributable to AllianceBernstein Unitholders and income taxes are recorded monthly using equity ownership interest as of each month-end, whereas the weighted average ownership interest shown in the table represents our quarter-end ownership interest. Accordingly, the calculation above will not compute to actual amounts recorded.