WEIGHTED AVERAGE NUMBER OF COMMON SHARES OUTSTANDING: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Earnings Per Share [Abstract] (LOSS) EARNINGS PER COMMON SHARE: Net Income (Loss) Attributable to Parent NET INCOME (LOSS) NET INCOME (LOSS) Net (loss) income Income Tax Expense (Benefit) (BENEFIT) PROVISION FOR INCOME TAXES Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest (LOSS) INCOME BEFORE INCOME TAXES Nonoperating Income (Expense) Total other expense, net Other Nonoperating Income (Expense) Other expense, net Interest Expense Interest expense Interest income Investment Income, Interest Nonoperating Income (Expense) [Abstract] OTHER (EXPENSE) INCOME: Operating Income (Loss) OPERATING (LOSS) INCOME Total expenses Costs and Expenses Selling, General and Administrative Expense Selling, general and administrative Research and Development Expense Research and development Cost of Goods Sold Cost of goods manufactured and sold EXPENSES: Costs and Expenses [Abstract] Total revenues Sales Revenue, Net Sales Revenue, Goods, Net Product sales, net Royalty Revenue Royalty revenues Manufacturing revenues Revenue Other Manufactured Products REVENUES: Sales Revenue, Net [Abstract] Non-voting Common Stock Non-voting Common Stock Consolidated Statements of Operations and Comprehensive (Loss) Income [Abstract] Consolidated Balance Sheets [Abstract] Prepaid expenses and other current assets Prepaid expenses and other current assets Prepaid expenses and other current assets. TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY Liabilities and Stockholders' Equity Stockholders' Equity Attributable to Parent Ending Balance, value Beginning Balance, value Total shareholders' equity Retained Earnings (Accumulated Deficit) Accumulated deficit Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss Additional Paid in Capital, Common Stock Additional paid-in capital Treasury Stock, Value Treasury stock, at cost (10,069,208 and 9,945,265 shares at March 31, 2011 and 2010, respectively) Common Stock, Value, Issued Common stock Stockholders' Equity Attributable to Parent [Abstract] SHAREHOLDERS' EQUITY: Commitments and Contingencies COMMITMENTS AND CONTINGENCIES (Note 15) Total liabilities Liabilities Other Liabilities, Noncurrent OTHER LONG-TERM LIABILITIES Deferred Revenue, Noncurrent DEFERRED REVENUE - LONG-TERM Total current liabilities Liabilities, Current Deferred Revenue, Current Deferred revenue - current Accounts Payable and Accrued Liabilities, Current Accounts payable and accrued expenses CURRENT LIABILITIES: Liabilities, Current [Abstract] Liabilities and Stockholders' Equity [Abstract] LIABILITIES AND SHAREHOLDERS' EQUITY TOTAL ASSETS Assets Other Assets, Noncurrent OTHER ASSETS Property, Plant and Equipment, Net PROPERTY, PLANT AND EQUIPMENT, NET Total current assets Assets, Current Inventory, Net Inventory Receivables, Net, Current Receivables Cash and Cash Equivalents, at Carrying Value CASH AND CASH EQUIVALENTS - End of period CASH AND CASH EQUIVALENTS - Beginning of period Cash and cash equivalents CURRENT ASSETS: Assets, Current [Abstract] ASSETS Assets [Abstract] Treasury Stock, Shares Treasury stock, shares Common stock, par value Common Stock, Par or Stated Value Per Share Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Shares, Issued Common stock, shares issued Common Stock, Shares, Outstanding Common stock, shares outstanding Fair Value Measurements [Abstract] Fair Value Measurements. FAIR VALUE MEASUREMENTS Fair Value Disclosures [Text Block] Income Taxes [Abstract] INCOME TAXES Income Tax Disclosure [Text Block] SHARE-BASED COMPENSATION Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Earnings Per Share [Text Block] EARNINGS PER SHARE Commitments and Contingencies [Abstract] Commitments And Contingencies. COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] PROPERTY, PLANT AND EQUIPMENT Property, Plant and Equipment Disclosure [Text Block] Statement [Table] Class of Stock [Axis] Class of Stock [Domain] Common Stock Common Stock Statement [Line Items] Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Public Float Entity Common Stock, Shares Outstanding Consolidated Statements of Cash Flows [Abstract] Property, Plant and Equipment [Abstract] Share-Based Compensation [Abstract] Restructuring [Abstract] RESTRUCTURING Restructuring and Related Activities Disclosure [Text Block] Accounts Payable and Accrued Expenses [Abstract] ACCOUNTS PAYABLE AND ACCRUED EXPENSES Accounts Payable and Accrued Liabilities Disclosure [Text Block] INVENTORY Inventory Disclosure [Text Block] Inventory [Abstract] Increase Decrease In Inventory, prepaid expenses and other assets Inventory, prepaid expenses and other assets Increase Decrease In Inventory, prepaid expenses and other assets. Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options Proceeds from the issuance of common stock for share-based compensation arrangements Non-cash investing and financing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] SUPPLEMENTAL CASH FLOW DISCLOSURE: Supplemental Cash Flow Information [Abstract] Cash and Cash Equivalents, Period Increase (Decrease) NET DECREASE IN CASH AND CASH EQUIVALENTS Net Cash Provided by (Used in) Financing Activities Cash flows used-in financing activities Payments for Repurchase of Common Stock Purchase of common stock for treasury CASH FLOWS FROM FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities [Abstract] Net Cash Provided by (Used in) Investing Activities Cash flows provided by investing activities Proceeds from Sale of Property, Plant, and Equipment Proceeds from the sale of equipment Payments to Acquire Property, Plant, and Equipment Additions to property, plant and equipment CASH FLOWS FROM INVESTING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] Net Cash Provided by (Used in) Operating Activities Cash flows (used in) provided by operating activities Deferred revenue Increase (Decrease) in Deferred Revenue Increase (Decrease) in Accounts Payable and Accrued Liabilities Accounts payable and accrued expenses Increase (Decrease) in Receivables Receivables Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Other non-cash charges Other Noncash Expense Share-based Compensation Share-based compensation expense Depreciation Depreciation Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to cash flows from operating activities: Available-for-sale Securities, Debt Securities, Current Investments - short-term Marketable Securities, Noncurrent INVESTMENTS - LONG-TERM Other long-term liabilities Increase (Decrease) in Other Operating Liabilities Payments to Acquire Marketable Securities Purchases of investments Proceeds from Sale and Maturity of Marketable Securities Sales and maturities of investments Cash paid for interest Interest Paid Cash paid for taxes Income Taxes Paid Noncash or Part Noncash Acquisition, Value of Liabilities Assumed Purchased capital expenditures included in accounts payable and accrued expenses Summary of Significant Accounting Policies [Abstract] INVESTMENTS Marketable Securities [Text Block] Investments [Abstract] Debt Instrument, Interest Rate, Stated Percentage RISPERDAL CONSTA Secured Notes, percentage RISPERDAL CONSTA Secured Notes Percentage RISPERDAL CONSTA secured notes, principal RISPERDAL CONSTA Secured Notes Percentage. Research and development revenue under collaborative arrangements Contracts Revenue Other Notes Payable, Current Non-recourse RISPERDAL CONSTA secured 7% notes - current Net Collaborative Profit Net collaborative profit Revenue earned during the period under the license and collaboration agreement with Cephalon, Inc. for the sale of Vivitrol in the U.S. Document Fiscal Year Focus Document Fiscal Period Focus Document and Entity Information [Abstract] Document and Entity Information. Payment of non recourse Product secured Seven Percent notes principal attributable to original issue discount Payment or purchase of non-recourse RISPERDAL CONSTA secured 7% notes attributable to original issue discount Payment of non-recourse 7% notes principal attributable to original issue discount. Earnings Per Share, Basic Basic Weighted Average Number of Shares Outstanding, Basic Basic Payments to Acquire Other Investments Investment in Acceleron Pharmaceuticals, Inc. Long-Term Debt [Abstract] Long-term Debt [Text Block] LONG-TERM DEBT Earnings Per Share, Diluted Diluted Weighted Average Number of Shares Outstanding, Diluted Diluted Comprehensive Income, Net of Tax, Attributable to Parent [Abstract] COMPREHENSIVE (LOSS) INCOME: Other Comprehensive Income, Available-for-sale Securities Adjustment, Net of Tax [Abstract] Unrealized losses on marketable securities: Other Comprehensive Income, Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Holding gains (losses), net of tax Other Comprehensive Income, Reclassification Adjustment for Write-down of Securities Included in Net Income, Net of Tax Less: Reclassification adjustment for losses included in net (loss) income Other Comprehensive Income, Available-for-sale Securities Adjustment, Net of Tax Unrealized gains (losses) on marketable securities Unrealized gain/(loss) on marketable securities, net of tax $1,831 for 2010 and $225 for 2011 Comprehensive Income, Net of Tax, Attributable to Parent COMPREHENSIVE (LOSS) INCOME Increase Decrease In Unearned Milestone Revenue Unearned milestone revenue Unearned milestone revenue. Excess Tax Benefit from Share-based Compensation, Financing Activities Excess tax benefit from share-based compensation COLLABORATIVE ARRANGEMENTS [Abstract] Collaborative arrangements. Collaborative Arrangements Text Block COLLABORATIVE ARRANGEMENTS Collaborative arrangements. Shareholders' Equity [Abstract] Stockholders' Equity Note Disclosure [Text Block] SHAREHOLDERS' EQUITY The Company [Abstract] Nature of operation Nature of Operations [Text Block] THE COMPANY Shares, Issued Ending Balance, shares Beginning Balance, shares Treasury Stock Value Acquired Cost Method Repurchase of common stock for treasury, at cost, value Adjustments to Additional Paid in Capital, Tax Effect from Share-based Compensation Excess tax benefit from share-based compensation Treasury Stock, Shares, Acquired Repurchase of common stock for treasury, at cost, shares Other Comprehensive Income, Available-for-sale Securities, Tax Tax effect on unrealized gain (loss) on marketable securities Accumulated Net Unrealized Investment Gain (Loss) [Member] Unrealized Gain/(Loss) on Marketable Securities Accumulated Translation Adjustment [Member] Foreign Currency Translation Adjustments Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Income Parent [Member] Parent Additional Paid-in Capital [Member] Additional Paid-In Capital Treasury Stock [Member] Treasury Stock Retained Earnings [Member] Accumulated Deficit Statement of Stockholders' Equity [Abstract] Statement, Equity Components [Axis] Equity Component [Domain] Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Value Share-based compensation Available-for-sale Securities, Gross Realized Losses Realized losses on investments Gains (Losses) on Extinguishment of Debt Loss on purchase of non-recourse RISPERDAL CONSTA secured 7% Notes Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities Payment of debt and capital leases Repayments of Notes Payable Payment or purchase of non-recourse RISPERDAL CONSTA secured 7% notes Stock Issued During Period, Value, Share-based Compensation Issuance of common stock under employee stock plans, value Stock Issued During Period, Shares, Share-based Compensation Issuance of common stock under employee stock plans, shares Proceeds From Sale Of Other Investments Proceeds from the sale of investment in Reliant Pharmaceuticals, Inc. Receipt Of Company Stock For Purchase Of Stock Options Or To Satisfy Minimum Tax Withholding Obligations Related To Stock Based Awards Shares Receipt of Alkermes' stock for the purchase of stock options or to satisfy minimum tax withholding obligations related to stock based awards, shares Receipt of company stock for the purchase of stock options or to satisfy minimum tax withholding obligations related to stock based awards shares. Receipt Of Company Stock For Purchase Of Stock Options Or To Satisfy Minimum Tax Withholding Obligations Related To Stock Based Awards Value Receipt of Alkermes' stock for the purchase of stock options or to satisfy minimum tax withholding obligations related to stock based awards, value Receipt of company stock for the purchase of stock options or to satisfy minimum tax withholding obligations related to stock based awards value. Noncash or Part Noncash Acquisition, Investments Acquired Investment in Civitas Therapeutics, Inc. Subsequent Events [Abstract] Subsequent events. Schedule of Subsequent Events [Text Block] SUBSEQUENT EVENTS