Related Party Transactions (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues:
Investment advisory and services fees		$ 1,916,419,000	$ 2,051,692,000	$ 1,920,332,000
Bernstein research services		437,414,000	430,521,000	434,605,000
Other revenues		107,569,000	109,803,000	107,848,000
Total revenues		2,752,441,000	2,952,105,000	2,911,290,000
Expenses:
Commissions and distribution payments to financial intermediaries		302,684,000	286,676,000	234,203,000
Other		217,598,000	192,096,000	176,703,000
General and administrative		533,578,000	516,185,000	520,372,000
Total expenses		2,958,360,000	2,489,695,000	2,316,051,000
Balance Sheet:
Institutional investment advisory and services fees receivable		265,248,000	343,473,000
Ownership interest in consolidated joint venture purchased from unaffiliated third party (in hundredths)	50.00%
Revenues [Abstract]
AXA minority interest recorded in Australian joint venture		(36,799,000)	(15,320,000)	22,381,000
Consolidated private equity fund		618,924,000	457,850,000
Limited partnership interest held in AllianceBernstein Venture I, L.P. (in hundredths)		10.00%
Investment advisory and services fees		1,916,419,000	2,051,692,000	1,920,332,000
Distribution revenues		351,621,000	338,597,000	277,328,000
Other revenues		107,569,000	109,803,000	107,848,000
Bernstein research services		437,414,000	430,521,000	434,605,000
Capital contributions from general partner		4,793,000	4,879,000	4,905,000
Due to Holding, net		5,479,000	1,277,000	0
Due from Holding, net		0	0	1,484,000
AXA And Its Subsidiaries [Member]
Related Party Transaction [Line Items]
Sales of company-sponsored mutual funds		400,000,000	500,000,000	300,000,000
Revenues:
Investment advisory and services fees		114,266,000	135,004,000	131,181,000
Bernstein research services		802,000	492,000	71,000
Other revenues		599,000	583,000	568,000
Total revenues		115,667,000	136,079,000	131,820,000
Expenses:
Commissions and distribution payments to financial intermediaries		7,411,000	8,896,000	8,637,000
Other		1,467,000	264,000	368,000
General and administrative		22,191,000	21,256,000	17,285,000
Total expenses		31,069,000	30,416,000	26,290,000
Balance Sheet:
Institutional investment advisory and services fees receivable		9,004,000	18,654,000	11,287,000
Other due (to) from AXA and its subsidiaries		(4,319,000)	(4,732,000)	(3,888,000)
Prepaid insurance		1,411,000	1,199,000	1,199,000
Total		6,096,000	15,121,000	8,598,000
Ownership interest in consolidated joint venture sold by AXA (in hundredths)	50.00%
Revenues [Abstract]
AXA minority interest recorded in Australian joint venture	400,000		3,600,000	3,700,000
Investment advisory and services fees		114,266,000	135,004,000	131,181,000
Other revenues		599,000	583,000	568,000
Bernstein research services		802,000	492,000	71,000
Australian Joint Venture [Member]
Revenues [Abstract]
Investment advisory and services fees	8,500,000		37,100,000	40,900,000
AXA Interest In Australian Joint Venture [Member]
Revenues [Abstract]
Investment advisory and services fees	3,000,000		12,800,000	14,000,000
AllianceBernstein Venture Fund I, L.P. [Member]
Revenues [Abstract]
Consolidated private equity fund		59,000,000	101,000,000	163,000,000
Limited partnership interest held in AllianceBernstein Venture I, L.P. (in hundredths)		10.00%
Mutual Fund [Member]
Revenues:
Investment advisory and services fees		864,578,000	809,387,000	643,953,000
Bernstein research services		81,000	121,000	1,138,000
Other revenues		5,643,000	5,726,000	6,962,000
Revenues [Abstract]
Investment advisory and services fees		864,578,000	809,387,000	643,953,000
Distribution revenues		351,621,000	338,597,000	277,328,000
Shareholder servicing fees		91,931,000	93,148,000	90,141,000
Other revenues		5,643,000	5,726,000	6,962,000
Bernstein research services		$ 81,000	$ 121,000	$ 1,138,000