Document and Entity Information	12 Months Ended
	Dec. 31, 2018 USD ($) shares
Document and Entity Information [Abstract]
Entity Registrant Name	ALLIANCEBERNSTEIN L.P.
Entity Central Index Key	0001109448
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float | $	$ 0
Entity Common Stock, Shares Outstanding | shares	268,850,276
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	false