Consolidated Statements of Operations - USD ($) shares 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
Income Statement [Abstract]
Net sales	$ 197,519,000	$ 188,029,000	$ 187,308,000	$ 184,935,000	$ 183,926,000	$ 177,184,000	$ 186,123,000	$ 187,590,000	$ 757,791,000	$ 734,823,000	$ 823,192,000
Operating costs and expenses:
Cost of sales									571,679,000	571,543,000	663,683,000
Selling, general and administrative expenses									107,868,000	101,446,000	98,533,000
Research and development									27,629,000	24,955,000	25,802,000
Restructuring charges									5,404,000	4,178,000	13,017,000
Write down of long-lived assets									10,279,000	0	0
Net (gain) loss on sales and disposals of assets									392,000	375,000	(221,000)
Total operating costs and expenses									723,251,000	702,497,000	800,814,000
Operating income (loss)	8,742,000	13,850,000	3,050,000	8,898,000	8,603,000	8,493,000	13,987,000	1,243,000	34,540,000	32,326,000	22,378,000
Other (income) expense:
Interest income									(24,000)	(14,000)	(15,000)
Interest expense									39,755,000	39,605,000	40,701,000
Change in value of TOKIN options									(10,700,000)	26,300,000	(2,100,000)
Non-operating (income) expense, net									(5,127,000)	(2,348,000)	(4,082,000)
Income (loss) from continuing operations before income taxes and equity income (loss) from TOKIN									10,636,000	(31,217,000)	(12,126,000)
Income tax expense (benefit)									4,290,000	6,006,000	5,227,000
Income (loss) from continuing operations before equity income (loss) from TOKIN									6,346,000	(37,223,000)	(17,353,000)
Equity income (loss) from TOKIN									41,643,000	(16,406,000)	(2,169,000)
Income (loss) from continuing operations									47,989,000	(53,629,000)	(19,522,000)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									0	0	5,379,000
Net income (loss)	$ 52,914,000	$ 12,278,000	$ (4,998,000)	$ (12,205,000)	$ (15,173,000)	$ (8,600,000)	$ 7,194,000	$ (37,050,000)	$ 47,989,000	$ (53,629,000)	$ (14,143,000)
Net income (loss) per basic share:
Loss from continuing operations (in dollars per share)									$ 1.03	$ (1.17)	$ (0.43)
Income (loss) from discontinued operations (in dollars per share)									0.00	0.00	0.12
Net income (loss) (in dollars per share)	$ 1.13	$ 0.26	$ (0.11)	$ (0.26)	$ (0.33)	$ (0.19)	$ 0.16	$ (0.81)	1.03	(1.17)	(0.31)
Net income (loss) per diluted share:
Loss from continuing operations (in dollars per share)									0.87	(1.17)	(0.43)
Income (loss) from discontinued operations (in dollars per share)									0.00	0.00	0.12
Net income (loss) (in dollars per share)	$ 0.93	$ 0.22	$ (0.11)	$ (0.26)	$ (0.32)	$ (0.19)	$ 0.14	$ (0.80)	$ 0.87	$ (1.17)	$ (0.31)
Weighted-average shares outstanding:
Basic (in shares)									46,552	46,004	45,381
Diluted (in shares)									55,389	46,004	45,381