Debt (Details) (USD $)				1 Months Ended	12 Months Ended					12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 09, 2010	Jan. 17, 2012 Line of Credit [Member]	Dec. 31, 2011 Line of Credit [Member]	Dec. 31, 2010 Line of Credit [Member]	Dec. 31, 2011 Line of Credit [Member] Subsidiaries [Member]	Dec. 09, 2010 Line of Credit [Member] Subsidiaries [Member]	Dec. 09, 2010 Line of Credit [Member] Parent Company [Member]	Dec. 31, 2011 Commercial Paper [Member]	Dec. 31, 2010 Commercial Paper [Member]
Short-term Debt [Line Items]
Short-term debt outstanding	$ 444,903,000	$ 224,991,000				$ 0				$ 444,900,000	$ 225,000,000
Weighted average interest rates on short-term debt outstanding (in hundredths)										0.20%	0.30%
Average daily borrowings					6,400,000	2,400,000				273,600,000	104,200,000
Weighted average interest rates on average daily borrowings (in hundredths)					1.30%	1.50%				0.20%	0.20%
Revolving credit facility description				On January 17, 2012, the 2010 Credit Facility was amended and restated. The principal amount was amended to 900 million from the original principal amount of 1.0 billion. Also, the amendment increased the accordion feature from 250 million to 350 million. In addition, the maturity date of the 2010 Credit Facility was extended from December 9, 2013 to January 17, 2017. There were no other significant changes in terms and conditions included in this amendment.	On December 9, 2010, AllianceBernstein entered into a committed, unsecured three-year senior revolving credit facility the “2010 Credit Facility” with a group of commercial banks and other lenders in an original principal amount of 1.0 billion with SCB LLC as an additional borrower. The 2010 Credit Facility replaced AllianceBernstein's existing 1.95 billion of committed credit lines comprised of two separate lines – a 1.0 billion committed, unsecured revolving credit facility in the name of AllianceBernstein, which had a scheduled expiration date of February 17, 2011, and SCB LLC's 950 million committed, unsecured revolving credit facility, which had a scheduled expiration date of January 25, 2011, both of which were terminated upon the effectiveness of the 2010 Credit Facility. AllianceBernstein has agreed to guarantee the obligations of SCB LLC under the 2010 Credit Facility.		SCB LLC has five uncommitted lines of credit with four financial institutions. Two of these lines of credit permit us to borrow up to an aggregate of approximately 200.0 million while three lines have no stated limit.
Credit Facility original principal	1,000,000,000	1,000,000,000		900,000,000
Replaced committed lines of credit - Maximum			1,950,000,000					950,000,000	1,000,000,000
Credit Facility - Incremental increases in principal				350,000,000	250,000,000		200,000,000
Line of credit facility average borrowings					$ 100,000	$ 65,600,000
Weighted average interest rate (in hundredths)					1.30%	0.30%
Uncommitted lines of credit with financial institutions							5
Financial institutions with uncommitted lines of credit							4
Lines of credit with aggregate borrowing capacity							2
Lines of credit no stated limit							3