Income Taxes Tax credit carryforward (Details) (USD $)	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Tax Credit Carryforward [Line Items]
Income Tax Holiday, Aggregate Dollar Amount	$ 6,500,000	$ 20,900,000	$ 17,300,000
Income Tax Holiday, Income Tax Benefits Per Share	$ 0.03	$ 0.10	$ 0.09
State and Local Jurisdiction [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	53,200,000
Tax Credit Carryforward, Expiration Dates	2012 and 2027
Tax Credit Carryforward, Valuation Allowance	53,200,000
Foreign Country [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	20,000,000
Tax Credit Carryforward, Expiration Dates	2013 and 2017
Tax Credit Carryforward, Valuation Allowance	19,900,000
Research [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	28,500,000
Tax Credit Carryforward, Expiration Dates	2017 and 2032
Alternative Minimum Tax [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	$ 2,200,000