Commitments (Details) (USD $)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Future minimum lease commitments under operating leases [Abstract]
Operating Leases, Future Minimum Payments Due, Current	$ 13,323,000
Operating Leases, Future Minimum Payments, Due in Two Years	11,510,000
Operating Leases, Future Minimum Payments, Due in Three Years	10,171,000
Operating Leases, Future Minimum Payments, Due in Four Years	8,910,000
Operating Leases, Future Minimum Payments, Due in Five Years	7,577,000
Operating Leases, Future Minimum Payments, Due Thereafter	18,692,000
Operating Leases, Total Future Minimum Payments Due	70,183,000
Rental expense under operating lease	20,300,000	15,100,000	13,000,000
Property, Plant and Equipment Purchase Commitment [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	28,000,000
Purchase Commitment, Other Obligations [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	57,700,000
Wafer Foundry Purchase Commitment [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	$ 55,300,000