Document and Entity Information (USD $)	12 Months Ended
	Mar. 31, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	FOREST LABORATORIES INC
Entity Central Index Key	0000038074
Current Fiscal Year End Date	--03-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float	$ 9,375,131,945
Entity Common Stock, Shares Outstanding	266,669,865
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Mar. 31, 2013