Annual report pursuant to Section 13 and 15(d)

Income Taxes (Details 2)

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Income Taxes (Details 2) (USD $)
12 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Mar. 31, 2011
NOL and tax credit carry forwards for federal and state income tax purposes      
Period of time from grant date during which a tax benefit may be generated from a premature disposition of option shares exercised 2 years    
Period of time from exercise date during which a tax benefit may be generated from a premature disposition of option shares exercised 1 year    
Federal and state NOL carryforwards generated by disqualifying dispositions of stock options and exercises of nonqualified stock options $ 27,700,000    
Tax benefits associated with the stock options excluded from the provision for income taxes and credited directly to additional paid-in-capital 10,400,000    
Other disclosures      
Interest or penalties related to unrecognized tax benefits 0 0  
Amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate 2,400,000 2,100,000  
Reconciliation of the beginning and ending amount of total gross unrecognized tax benefits      
Balance at the beginning of the period 2,148,000 1,973,000 1,806,000
Gross decrease related to prior year tax positions (100,000)    
Gross increase related to prior year tax positions 222,000    
Gross increase related to current year tax positions 148,000 175,000 167,000
Lapse of statute of limitations 0    
Balance at the end of the period 2,418,000 2,148,000 1,973,000
Maximum
     
NOL and tax credit carry forwards for federal and state income tax purposes      
Annual limitation amount on utilization of the NOLs and tax credits 57,300,000    
Federal
     
NOL and tax credit carry forwards for federal and state income tax purposes      
Deferred tax assets related to research and development credits 9,600,000 9,100,000  
NOL 592,005,000    
Tax credit carry forwards 9,577,000    
State
     
NOL and tax credit carry forwards for federal and state income tax purposes      
Deferred tax assets related to research and development credits 8,700,000 7,900,000  
NOL 283,866,000    
Tax credit carry forwards $ 8,718,000