Net Capital (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Stanford C. Bernstein & Co.,LLC [Member]
Computation of Net Capital or Financial Resource Requirement [Abstract]
Minimum net capital required per stock exchange and SEC rules	$ 1
Alternative method of calculating aggregate debit items arising from customer transactions permitted by rule (in hundredths)	2.00%
Alternative net capital	111.3
Alternative excess net capital	96.0
Alternative net capital requirement	15.3
Stanford C. Bernstein Limited [Member]
Computation of Net Capital or Financial Resource Requirement [Abstract]
Aggregate regulatory financial resources	47.0
Actual capital or financial resources in excess of minimum requirement	30.5
Financial resource requirements per London stock exchange rules, per calculation	16.5
Alliance Bernstein Investments [Member] | US Securities And Exchange Commission [Member]
Computation of Net Capital or Financial Resource Requirement [Abstract]
Net capital	46.2
Actual net capital in excess of the minimum net capital required	46.1
Net capital required per stock rules, per calculation	$ 0.1