The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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- Definition

This element represents the total of accruals as of the date of the statement of financial position for interest recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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Income Taxes - Additional Information (Details) (USD $)	12 Months Ended
Income Taxes - Additional Information (Details) (USD $)	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Income Tax Contingency [Line Items]
Tax at federal statutory rate	35.00%	35.00%	35.00%
Unrecognized tax benefits	$ 43,382,000	$ 43,179,000
Unrecognized tax benefits that would impact effective tax rate	600,000
Accrued interest and penalties recognized	100,000
2018 \| Internal Revenue Service (IRS) [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	1,124,400,000
2013 \| State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	652,100,000
Research Tax Credit Carryforward [Member] \| Internal Revenue Service (IRS) [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	59,800,000
Research Tax Credit Carryforward [Member] \| State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	$ 29,000,000