Basis of Financial Statement Presentation (Details) Share data in Millions, unless otherwise specified	3 Months Ended		6 Months Ended								6 Months Ended
	Sep. 30, 2013 USD ($)	Sep. 30, 2012	Sep. 30, 2013 USD ($)	Sep. 30, 2012	Mar. 31, 2013 USD ($)	Aug. 28, 2012 USD ($)	Aug. 31, 2006 USD ($)	Aug. 31, 2006 EUR (€)	Sep. 30, 2013 Carrying Value USD ($)	Mar. 31, 2013 Carrying Value USD ($)	Sep. 30, 2013 Recurring USD ($)	Sep. 30, 2013 Recurring Fair Value USD ($)	Mar. 31, 2013 Recurring Fair Value USD ($)	Sep. 30, 2013 Recurring Level 1 Fair Value USD ($)	Mar. 31, 2013 Recurring Level 1 Fair Value USD ($)	Sep. 30, 2013 Recurring Level 2 Fair Value USD ($)	Mar. 31, 2013 Recurring Level 2 Fair Value USD ($)	Sep. 30, 2013 Recurring Level 3 Fair Value USD ($)	Mar. 31, 2013 Recurring Level 3 Fair Value USD ($)
Restricted Cash
Prepayment received from an OEM						$ 24,000,000
Amount of prepayment utilized for purchase of manufacturing equipment			11,600,000
Prepayment received from an OEM classified as restricted cash	12,400,000		12,400,000
Guarantee issued by the European bank in conjunction with the establishment of a VAT registration in The Netherlands							2,000,000	1,500,000
Deposits pledged to European bank							2,200,000	1,700,000
Fair Value Measurement
Money markets									5,281,000	29,984,000		5,281,000	29,984,000	5,281,000	29,984,000
Long-term debt									403,278,000	383,500,000		357,779,000	393,928,000	315,950,000	369,200,000	41,829,000	24,728,000
NEC TOKIN options, net									106,000	489,000		106,000	489,000					106,000	489,000
NEC TOKIN option valuation activity using significant unobservable inputs (Level 3)
Balance at the beginning of the period											489,000
Change in value of NEC TOKIN options			(383,000)								(383,000)
Balance at the end of the period											106,000
Components of inventories
Raw materials and supplies	98,563,000		98,563,000		84,852,000
Work in process	68,798,000		68,798,000		70,522,000
Finished goods	67,996,000		67,996,000		68,705,000
Inventory, gross	235,357,000		235,357,000		224,079,000
Inventory reserves	(26,521,000)		(26,521,000)		(18,464,000)
Inventories, net	208,836,000		208,836,000		205,615,000
Reserve for inventory held by a third party			$ 3,900,000
Warrant
Number of shares subject to a warrant held by K Equity, LLC	8.4		8.4		8.4
Revenue Recognition
Period of product warranty			1 year
Warranty costs as a percentage of net sales, maximum	1.50%	1.50%	1.50%	1.50%