Condensed Consolidating Financial Statements - Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 197,519	$ 188,029	$ 187,308	$ 184,935	$ 183,926	$ 177,184	$ 186,123	$ 187,590	$ 757,791	$ 734,823	$ 823,192
Operating costs and expenses:
Cost of sales									571,679	571,543	663,683
Selling, general and administrative expenses									107,868	101,446	98,533
Research and development									27,629	24,955	25,802
Restructuring charges									5,404	4,178	13,017
Asset Impairment Charges									10,279	0	0
Write down of long-lived assets									10,279	0	0
Net (gain) loss on sales and disposals of assets									392	375	(221)
Total operating costs and expenses									723,251	702,497	800,814
Operating income (loss)	8,742	13,850	3,050	8,898	8,603	8,493	13,987	1,243	34,540	32,326	22,378
Interest income									(24)	(14)	(15)
Interest expense									39,755	39,605	40,701
Change in value of TOKIN options									(10,700)	26,300	(2,100)
Non-operating (income) expense, net									(5,127)	(2,348)	(4,082)
Equity in earnings of subsidiaries									0	0	0
Income (loss) from continuing operations before income taxes and equity income (loss) from TOKIN									10,636	(31,217)	(12,126)
Income tax expense (benefit)									4,290	6,006	5,227
Income (loss) from continuing operations before equity income (loss) from NEC TOKIN									6,346	(37,223)	(17,353)
Equity income (loss) from TOKIN									41,643	(16,406)	(2,169)
Income (loss) from continuing operations									47,989	(53,629)	(19,522)
Income (loss) from discontinued operations, net of income tax expense (benefit) of $0, $0, and $1,976, respectively									0	0	5,379
Net income (loss)	$ 52,914	$ 12,278	$ (4,998)	$ (12,205)	$ (15,173)	$ (8,600)	$ 7,194	$ (37,050)	47,989	(53,629)	(14,143)
Reclassifications and Eliminations
Condensed Financial Statements, Captions [Line Items]
Net sales									(813,899)	(835,030)	(929,212)
Operating costs and expenses:
Cost of sales									(759,432)	(780,156)	(869,707)
Selling, general and administrative expenses									(54,467)	(54,874)	(59,505)
Research and development									0	0	0
Restructuring charges									0	0	0
Asset Impairment Charges									0
Net (gain) loss on sales and disposals of assets									0	0	0
Total operating costs and expenses									(813,899)	(835,030)	(929,212)
Operating income (loss)									0	0	0
Interest income									0	0	0
Interest expense									0	0	0
Change in value of TOKIN options									0	0	0
Non-operating (income) expense, net									0	0	0
Equity in earnings of subsidiaries									91,186	(12,619)	27,998
Income (loss) from continuing operations before income taxes and equity income (loss) from TOKIN									(91,186)	12,619	(27,998)
Income tax expense (benefit)									0	0	0
Income (loss) from continuing operations before equity income (loss) from NEC TOKIN									(91,186)	12,619	(27,998)
Equity income (loss) from TOKIN									0	0	0
Income (loss) from continuing operations											(27,998)
Income (loss) from discontinued operations, net of income tax expense (benefit) of $0, $0, and $1,976, respectively											0
Net income (loss)									(91,186)	12,619	(27,998)
Parent
Condensed Financial Statements, Captions [Line Items]
Net sales									0	0	195
Operating costs and expenses:
Cost of sales									1,607	1,194	2,468
Selling, general and administrative expenses									44,447	38,071	41,783
Research and development									323	79	436
Restructuring charges									0	0	0
Asset Impairment Charges									0
Net (gain) loss on sales and disposals of assets									(299)	(7)	(10)
Total operating costs and expenses									46,078	39,337	44,677
Operating income (loss)									(46,078)	(39,337)	(44,482)
Interest income									0	0	0
Interest expense									37,606	37,856	38,632
Change in value of TOKIN options									0	0	0
Non-operating (income) expense, net									(40,487)	(36,183)	(40,903)
Equity in earnings of subsidiaries									(91,186)	12,619	(27,998)
Income (loss) from continuing operations before income taxes and equity income (loss) from TOKIN									47,989	(53,629)	(14,213)
Income tax expense (benefit)									0	0	(70)
Income (loss) from continuing operations before equity income (loss) from NEC TOKIN									47,989	(53,629)	(14,143)
Equity income (loss) from TOKIN									0	0	0
Income (loss) from continuing operations											(14,143)
Income (loss) from discontinued operations, net of income tax expense (benefit) of $0, $0, and $1,976, respectively											0
Net income (loss)									47,989	(53,629)	(14,143)
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales									860,428	866,163	978,705
Operating costs and expenses:
Cost of sales									683,103	708,143	823,429
Selling, general and administrative expenses									74,093	74,521	70,074
Research and development									18,073	17,313	17,588
Restructuring charges									3,901	2,564	3,310
Asset Impairment Charges									4,586
Net (gain) loss on sales and disposals of assets									1,405	(484)	181
Total operating costs and expenses									785,161	802,057	914,582
Operating income (loss)									75,267	64,106	64,123
Interest income									3	0	0
Interest expense									1,587	1,189	998
Change in value of TOKIN options									(10,700)	26,300	(2,100)
Non-operating (income) expense, net									40,527	34,188	49,069
Equity in earnings of subsidiaries									0	0	0
Income (loss) from continuing operations before income taxes and equity income (loss) from TOKIN									43,850	2,429	16,156
Income tax expense (benefit)									(65)	(269)	576
Income (loss) from continuing operations before equity income (loss) from NEC TOKIN									43,915	2,698	15,580
Equity income (loss) from TOKIN									41,643	(16,406)	(2,169)
Income (loss) from continuing operations											13,411
Income (loss) from discontinued operations, net of income tax expense (benefit) of $0, $0, and $1,976, respectively											102
Net income (loss)									85,558	(13,708)	13,513
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales									711,262	703,690	773,504
Operating costs and expenses:
Cost of sales									646,401	642,362	707,493
Selling, general and administrative expenses									43,795	43,728	46,181
Research and development									9,233	7,563	7,778
Restructuring charges									1,503	1,614	9,707
Asset Impairment Charges									5,693
Net (gain) loss on sales and disposals of assets									(714)	866	(392)
Total operating costs and expenses									705,911	696,133	770,767
Operating income (loss)									5,351	7,557	2,737
Interest income									(27)	(14)	(15)
Interest expense									562	560	1,071
Change in value of TOKIN options									0	0	0
Non-operating (income) expense, net									(5,167)	(353)	(12,248)
Equity in earnings of subsidiaries									0	0	0
Income (loss) from continuing operations before income taxes and equity income (loss) from TOKIN									9,983	7,364	13,929
Income tax expense (benefit)									4,355	6,275	4,721
Income (loss) from continuing operations before equity income (loss) from NEC TOKIN									5,628	1,089	9,208
Equity income (loss) from TOKIN									0	0	0
Income (loss) from continuing operations											9,208
Income (loss) from discontinued operations, net of income tax expense (benefit) of $0, $0, and $1,976, respectively											5,277
Net income (loss)									$ 5,628	$ 1,089	$ 14,485