INCOME TAXES (Details 3) (USD $)	Mar. 31, 2013	Mar. 31, 2012
Deferred tax assets :
Tax benefit from the exercise of stock options	$ 8,437,000	$ 22,089,000
Share-based compensation	23,468,000	21,992,000
Tax credit carryforwards	10,543,000	12,294,000
Deferred revenue	1,682,000	1,778,000
Intangible assets	277,000	748,000
Property, plant and equipment	653,000
Bonus accrual	7,034,000	5,849,000
Other	9,150,000	9,774,000
Less: valuation allowance	(86,714,000)	(107,128,000)
Total deferred tax assets	30,868,000	28,763,000
Deferred tax liabilities :
Intangible assets	(40,968,000)	(43,606,000)
Property, plant and equipment	(19,607,000)	(19,049,000)
Other	(2,072,000)
Total deferred tax liabilities	(62,647,000)	(62,655,000)
Net deferred tax liabilities	(31,779,000)	(33,892,000)
Schedule of current and non-current deferred tax assets (liabilities)
Current deferred tax assets	5,824,000	656,000
Current deferred tax liabilities		(36,000)
Non-current deferred tax liabilities	(37,603,000)	(34,512,000)
Net deferred tax liabilities	(31,779,000)	(33,892,000)
Alkermes Europe Ltd
Income taxes
NOL carryforwards		4,675,000
Ireland
Income taxes
Operating loss carryforwards	438,200,000
NOL carryforwards	55,842,000	55,176,000
Federal
Income taxes
Operating loss carryforwards	70,400,000
Amount of operating loss and tax credit carryforwards subject to annual limitation.	127,000,000
State
Income taxes
Operating loss carryforwards	8,700,000
Federal, State, and Local
Income taxes
NOL carryforwards	$ 496,000	$ 1,516,000