Basis of Financial Statement Presentation (Details) - USD ($) shares in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Mar. 31, 2016
Segment Reporting, Other Significant Reconciling Item, Consolidated [Abstract]
Other assets					$ 3,068,000
Total assets	$ 676,975,000		$ 676,975,000		699,780,000
Long-term debt, less current portion	386,098,000		386,098,000		385,833,000
Total liabilities and stockholders’ equity	676,975,000		676,975,000		699,780,000
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Money markets	640,000		640,000		738,000
Total debt	(386,098,000)		(386,098,000)		(387,833,000)
NEC TOKIN option, net	(31,000,000)		(31,000,000)		(20,600,000)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Change in value of NEC TOKIN option	(1,600,000)	$ (2,200,000)	10,400,000	$ 27,000,000
Inventory, Gross [Abstract]
Raw materials and supplies	75,211,000		75,211,000		80,289,000
Work in process	50,081,000		50,081,000		46,631,000
Finished goods	55,698,000		55,698,000		58,060,000
Inventory, gross	180,990,000		180,990,000		184,980,000
Inventory reserves	(16,013,000)		(16,013,000)		(16,101,000)
Inventories, net	$ 164,977,000		$ 164,977,000		$ 168,879,000
Warrant
Number of shares subject to a warrant held by K Equity, LLC	8.4		8.4		8.4
Revenue Recognition
Maximum Percentage of Purchased Inventory that Can be Returned by Distributor			6.00%
Period of product warranty			1 year
Warranty costs as a percentage of net sales, maximum	1.00%	1.00%	1.00%	1.00%
Recurring
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Total debt, fair value	$ (384,352,000)		$ (384,352,000)		$ (284,261,000)
NEC TOKIN option, net, fair value	(31,000,000)		(31,000,000)		(20,600,000)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance			(20,600,000)
Change in value of NEC TOKIN option			(10,400,000)
Ending balance	(31,000,000)		(31,000,000)
Recurring | Money Market Funds [Member]
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Money markets, fair value	640,000		640,000		738,000
Recurring | Level 1
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Total debt, fair value	(354,987,000)		(354,987,000)		(254,713,000)
Recurring | Level 1 | Money Market Funds [Member]
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Money markets, fair value	640,000		640,000		738,000
Recurring | Level 2
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Total debt, fair value	(29,365,000)		(29,365,000)		(29,548,000)
Recurring | Level 2 | Money Market Funds [Member]
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Money markets, fair value	0		0		0
Recurring | Level 3
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Total debt, fair value	0		0		0
NEC TOKIN option, net, fair value	(31,000,000)		(31,000,000)		(20,600,000)
Recurring | Level 3 | Money Market Funds [Member]
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Money markets, fair value	$ 0		$ 0		0
Restatement Adjustment [Member] | Accounting Standards Update 2015-03 [Member]
Segment Reporting, Other Significant Reconciling Item, Consolidated [Abstract]
Other assets					(2,764,000)
Total assets					(2,764,000)
Long-term debt, less current portion					(2,764,000)
Total liabilities and stockholders’ equity					(2,764,000)
Scenario, Previously Reported [Member]
Segment Reporting, Other Significant Reconciling Item, Consolidated [Abstract]
Other assets					5,832,000
Total assets					702,544,000
Long-term debt, less current portion					388,597,000
Total liabilities and stockholders’ equity					702,544,000
New Accounting Pronouncement, Early Adoption, Effect [Member] | Retained Earnings [Member] | Accounting Standards Update 2016-09 [Member]
Fair Value Measurement
Cumulative effect of new accounting principle in period of adoption					$ 130,000