Condensed Consolidating Financial Statements Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Revenues [Abstract]
Net sales	$ 188,029		$ 177,184	$ 560,272	$ 550,897
Operating costs and expenses:
Cost of sales	140,692		138,436	423,999	429,630
Selling, general and administrative expenses	26,665		22,278	78,551	75,656
Research and development	7,059		6,134	21,107	18,560
Restructuring charges	(369)		1,714	4,317	3,561
Write down of long-lived assets	0	$ 6,200	0	6,193	0
Net (gain) loss on sales and disposals of assets	132		129	307	(233)
Total operating costs and expenses	174,179		168,691	534,474	527,174
Operating income (loss)	13,850		8,493	25,798	23,723
Interest income	(5)		(4)	(14)	(10)
Interest expense	9,918		9,852	29,751	29,676
Change in value of NEC TOKIN option	(6,900)		(700)	3,500	26,300
Other (income) expense, net	3,384		1,320	6,683	2,495
Equity in earnings of subsidiaries	0		0	0	0
Income (loss) from before income taxes and equity income (loss) from NEC TOKIN	14,221		665	(756)	(29,748)
Income tax expense (benefit)	1,810		2,760	4,440	3,950
Income (loss) before equity income (loss) from NEC TOKIN	12,411		(2,095)	(5,196)	(33,698)
Equity income (loss) from NEC TOKIN	(133)		(6,505)	271	(4,758)
Net income (loss)	12,278		(8,600)	(4,925)	(38,456)
Reclassifications and Eliminations
Revenues [Abstract]
Net sales	(203,106)		(204,615)	(601,795)	(632,515)
Operating costs and expenses:
Cost of sales	(189,691)		(191,833)	(562,337)	(590,274)
Selling, general and administrative expenses	(13,415)		(12,782)	(39,459)	(42,241)
Research and development	0		0	0	0
Restructuring charges	0		0	0	0
Write down of long-lived assets	0			0
Net (gain) loss on sales and disposals of assets	0		0	0	0
Total operating costs and expenses	(203,106)		(204,615)	(601,796)	(632,515)
Operating income (loss)	0		0	1	0
Interest income	0		0	0	0
Interest expense	0		0	0	0
Change in value of NEC TOKIN option	0		0	0	0
Other (income) expense, net	0		0	0	0
Equity in earnings of subsidiaries	(23,211)		(1,547)	(27,047)	7,567
Income (loss) from before income taxes and equity income (loss) from NEC TOKIN	(23,211)		(1,547)	(27,046)	7,567
Income tax expense (benefit)	0		0	0	0
Income (loss) before equity income (loss) from NEC TOKIN	(23,211)		(1,547)	(27,046)	7,567
Equity income (loss) from NEC TOKIN	0		0	0	0
Net income (loss)	(23,211)		(1,547)	(27,046)	7,567
Parent
Revenues [Abstract]
Net sales	0		0	0	0
Operating costs and expenses:
Cost of sales	257		232	1,023	931
Selling, general and administrative expenses	11,695		8,306	31,471	27,028
Research and development	72		79	228	26
Restructuring charges	0		0	0	0
Write down of long-lived assets	0			0
Net (gain) loss on sales and disposals of assets	(7)		0	(292)	(7)
Total operating costs and expenses	12,017		8,617	32,430	27,978
Operating income (loss)	(12,017)		(8,617)	(32,430)	(27,978)
Interest income	0		0	0	0
Interest expense	9,395		9,461	28,214	28,395
Change in value of NEC TOKIN option	0		0	0	0
Other (income) expense, net	10,479		7,931	28,672	25,484
Equity in earnings of subsidiaries	23,211		1,547	27,047	(7,567)
Income (loss) from before income taxes and equity income (loss) from NEC TOKIN	12,278		(8,600)	(4,925)	(38,456)
Income tax expense (benefit)	0		0	0	0
Income (loss) before equity income (loss) from NEC TOKIN	12,278		(8,600)	(4,925)	(38,456)
Equity income (loss) from NEC TOKIN	0		0	0	0
Net income (loss)	12,278		(8,600)	(4,925)	(38,456)
Guarantor Subsidiaries
Revenues [Abstract]
Net sales	211,214		211,268	642,253	655,808
Operating costs and expenses:
Cost of sales	163,260		173,368	499,922	528,352
Selling, general and administrative expenses	16,590		16,207	52,796	56,197
Research and development	4,708		4,232	13,581	12,834
Restructuring charges	(466)		726	3,125	2,182
Write down of long-lived assets	(1,608)			4,585
Net (gain) loss on sales and disposals of assets	109		(348)	1,132	(1,101)
Total operating costs and expenses	182,593		194,185	575,141	598,464
Operating income (loss)	28,621		17,083	67,112	57,344
Interest income	0		0	3	0
Interest expense	383		267	1,161	865
Change in value of NEC TOKIN option	(6,900)		(700)	3,500	26,300
Other (income) expense, net	(11,671)		(7,997)	(29,556)	(25,065)
Equity in earnings of subsidiaries	0		0	0	0
Income (loss) from before income taxes and equity income (loss) from NEC TOKIN	23,467		9,519	32,892	5,114
Income tax expense (benefit)	37		44	94	(320)
Income (loss) before equity income (loss) from NEC TOKIN	23,430		9,475	32,798	5,434
Equity income (loss) from NEC TOKIN	(133)		(6,505)	271	(4,758)
Net income (loss)	23,297		2,970	33,069	676
Non-Guarantor Subsidiaries
Revenues [Abstract]
Net sales	179,921		170,531	519,814	527,604
Operating costs and expenses:
Cost of sales	166,866		156,669	485,391	490,621
Selling, general and administrative expenses	11,795		10,547	33,743	34,672
Research and development	2,279		1,823	7,298	5,700
Restructuring charges	97		988	1,192	1,379
Write down of long-lived assets	1,608			1,608
Net (gain) loss on sales and disposals of assets	30		477	(533)	875
Total operating costs and expenses	182,675		170,504	528,699	533,247
Operating income (loss)	(2,754)		27	(8,885)	(5,643)
Interest income	(5)		(4)	(17)	(10)
Interest expense	140		124	376	416
Change in value of NEC TOKIN option	0		0	0	0
Other (income) expense, net	4,576		1,386	7,567	2,076
Equity in earnings of subsidiaries	0		0	0	0
Income (loss) from before income taxes and equity income (loss) from NEC TOKIN	1,687		1,293	(1,677)	(3,973)
Income tax expense (benefit)	1,773		2,716	4,346	4,270
Income (loss) before equity income (loss) from NEC TOKIN	(86)		(1,423)	(6,023)	(8,243)
Equity income (loss) from NEC TOKIN	0		0	0	0
Net income (loss)	$ (86)		$ (1,423)	$ (6,023)	$ (8,243)