Commitments (Details) (USD $)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Future minimum lease commitments under operating leases [Abstract]
Operating Leases, Future Minimum Payments Due, Current	$ 16,146,000
Operating Leases, Future Minimum Payments, Due in Two Years	10,587,000
Operating Leases, Future Minimum Payments, Due in Three Years	7,365,000
Operating Leases, Future Minimum Payments, Due in Four Years	4,388,000
Operating Leases, Future Minimum Payments, Due in Five Years	1,153,000
Operating Leases, Future Minimum Payments, Due Thereafter	0
Operating Leases, Total Future Minimum Payments Due	39,639,000
Rental expense under operating lease	23,800,000	21,500,000	20,300,000
Property, Plant and Equipment Purchase Commitment [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	56,500,000
Purchase Commitment, Other Obligations [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	50,300,000
Wafer Foundry Purchase Commitment [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	$ 48,800,000