Summary of Significant Accounting Policies (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended																12 Months Ended
	Jan. 20, 2012	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jan. 31, 2012
Variable Interest Entity [Abstract]
Number of collateralized debt obligations managed that meet the definition of a Variable Interest Entities due primarily to the lack of unilateral decision-making authority of the equity holders.		5																5
Number of collateralized debt obligation's concluded that our investment management contract does not represent a variable interest in.		4																4
Cash of the variable interest entity		$ 7,600,000																$ 7,600,000
Collateral investments (at fair value) of the variable interest entity		305,400,000																305,400,000
Notes payable (at amortized cost) of the variable interest entity		317,100,000																317,100,000
Variable interests in certain structured products and hedge funds		22,500,000																22,500,000
Our maximum exposure to loss is limited to our investment in these entities.		100,000																100,000
Collateralized Securities Transactions
Cash collateral on deposit with lenders		34,900,000								72,500,000								34,900,000	72,500,000
Cash collateral received from borrowers		151,600,000								42,200,000								151,600,000	42,200,000
Cash on deposit with clearing organizations for trade facilitation purposes		16,800,000								16,500,000								16,800,000	16,500,000
SCB LLC held U.S. Treasury Bills		38,000,000								35,000,000								38,000,000	35,000,000
Investments [Abstract]
Limited Partnership Interest in Venture Capital Fund (in hundredths)																		10.00%
Private equity investments owned outside of consolidated venture capital fund																		3
Private equity investments owned outside consolidated venture capital fund accounted for using cost method																		2
Goodwill on Consolidated Balance Sheet [Abstract]
Purchase Price for SCB, Inc., Cash Payment Portion		1,500,000,000																1,500,000,000
Purchase Price SCB, Inc., AllianceBernstein Units Issued (in units)																		40.8
Goodwill amount		3,000,000,000																3,000,000,000
Goodwill		2,954,668,000								2,939,170,000								2,954,668,000	2,939,170,000
Closing price of holding unit		$ 13.08																$ 13.08
Book value of holding unit		$ 14.33																$ 14.33
Intangible Assets, Net [Abstract]
Intangible assets, net accumulated amortization		189,661,000								205,862,000								189,661,000	205,862,000
Definite-lived intangible assets subject to amortization, net		187,200,000																187,200,000
Indefinite-lived intangible assets not subject to amortization		2,500,000																2,500,000
Intangible Assets Acquired, Estimated Useful Life (in years)																		20
Gross carrying amount of intangible assets		424,400,000								419,200,000								424,400,000	419,200,000
Accumulated Amortization of Intangible Assets		234,700,000								213,300,000								234,700,000	213,300,000
Amortization Expense on Intangible Assets																		21,400,000	21,300,000	21,100,000
Future estimated amortization expense [Abstract]
2012																		22,000,000
2013																		22,000,000
2014																		22,000,000
2015																		22,000,000
2016																		22,000,000
Deferred Compensation Plans [Abstract]
Employee allocation percentage maximum (in hundredths)		50.00%																50.00%
Deferred cash maximum per employee		250,000																250,000
Deferred awards vesting period (in years)																		4
Deferred compensation liability for the full dollar value of the awards		159,900,000																159,900,000
Reclassified liability to partners' capital		130,300,000																130,300,000
Non-cash deferred compensation charge		587,131,000																587,131,000	0	0
Percentage of unrecognized deferred incentive compensation expense recognized (in hundredths)		100.00%																100.00%
Holding Units Purchased in Period (in units)																		13.5	8.8
Dollar Amount Paid For Holding Units Acquired																		220,800,000	226,400,000
Open-market purchases of Holding Units (in units)																		11.1	7.4
Dollar Amount Paid for Open-Market Purchases of Holding Units																		192,100,000	195,300,000
Restricted Holding Unit Awards to Employees (in units)	8.7																	1.7	13.1
Unallocated Holding Units Remaining in Rabbi Trust (in units)		13.6																13.6			6.2
Foreign Currency Translations [Abstract]
Net foreign currency transaction gains (losses)																		(2,400,000)	1,300,000	(400,000)
Cash Distributions [Abstract]
Subsequent Cash Distribution, Declaration Date																		2012-02-10
Subsequent Cash Distribution, Amount																		47,700,000
Subsequent Cash Distribution, Distribution Declared (in dollars per unit)																		$ 0.17
General Partner partnership interest (in hundredths)																		1.00%
Subsequent Cash Distribution, Distribution Date																		2012-03-08
Subsequent Cash Distribution, Date of Record																		2012-02-21
Total cash distributions per Unit paid to the General Partner and unitholders (in dollars per share)		$ 0.17	[1],[2]	$ 0.32	[1]	$ 0.41	[1]	$ 0.48	[1]	$ 0.49	[1]	$ 0.18	[1]	$ 0.38	[1]	$ 0.53	[1]	$ 1.70	$ 1.79	$ 1.73
Real Estate Charges [Abstract]
Number of Square Feet (SFT) of Office Space Decided to Sub-lease in New York (in square feet)										380,000									380,000
Pre-tax Real Estate Charge as Part of Workforce Reduction																		7,200,000	101,700,000
Amount of Write-off of Leasehold Improvements, Furniture and Equipment Related to Space Sub-leased		3,000,000																3,000,000
London Real Estate Charge																		8,800,000
Payment to Assignee in fourth quarter																		5,800,000
Additional write-offs - New York																		1,500,000
Other restructuring costs																		400,000
Real Estate Liability Restructuring Reserve [Roll Forward]
Beginning Balance	71,164,000							89,793,000								0		89,793,000	0
Expense (credit) incurred																		(3,506,000)	76,177,000
Deferred rent																		2,288,000	22,954,000
Payments made																		(18,696,000)	(9,814,000)
Interest accretion																		1,285,000	476,000
Ending Balance		71,164,000								89,793,000								71,164,000	89,793,000	0
Sanford C Bernstein Inc Acquisition [Member]
Goodwill on Consolidated Balance Sheet [Abstract]
Goodwill amount		2,800,000,000																2,800,000,000
Intangible Assets, Net [Abstract]
Definite-lived intangible assets subject to amortization, net		181,100,000																181,100,000
Series of Individually Immaterial Business Acquisitions [Member]
Goodwill on Consolidated Balance Sheet [Abstract]
Goodwill amount		$ 154,000,000																$ 154,000,000
Furniture [Member]
Furniture, Equipment and Leasehold Improvements [Abstract]
Useful Life (in years)																		8
Equipment [Member]
Furniture, Equipment and Leasehold Improvements [Abstract]
Useful life minimum (in years)																		3
Useful life maximum (in years)																		6

[1] Declared and paid during the following quarter.

[2] The 2011 distribution excludes the $587.1 million one-time, non-cash deferred compensation charge.