Commitments (Details) (USD $)	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Future minimum lease commitments under operating leases [Abstract]
Operating Leases, Future Minimum Payments Due, Current	$ 9,293,000
Operating Leases, Future Minimum Payments, Due in Two Years	7,221,000
Operating Leases, Future Minimum Payments, Due in Three Years	4,594,000
Operating Leases, Future Minimum Payments, Due in Four Years	3,438,000
Operating Leases, Future Minimum Payments, Due in Five Years	3,238,000
Operating Leases, Future Minimum Payments, Due Thereafter	2,693,000
Operating Leases, Total Future Minimum Payments Due	30,477,000
Rental expense under operating lease	15,100,000	13,000,000	10,700,000
Property, Plant and Equipment Purchase Commitment [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	13,300,000
Purchase Commitment, Other Obligations [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	21,400,000
Wafer Foundry Purchase Commitment [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	$ 19,500,000