Segment and Geographic Information Segment and Geographic Information - Summarized Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Segment and geographic information
Assets	$ 702,544				$ 746,693				$ 702,544	$ 746,693
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property									(375)	221	$ (32)
Asset Impairment Charges									0	0	4,476
Restructuring charges									4,178	13,017	14,122
Net sales	183,926	$ 177,184	$ 186,123	$ 187,590	193,708	$ 201,310	$ 215,293	$ 212,881	734,823	823,192	833,666
Operating income (loss)	8,603	$ 8,493	$ 13,987	$ 1,243	912	$ 9,302	$ 12,770	$ (606)	32,326	22,378	(18,211)
Depreciation and amortization									39,016	40,768	49,527
Additions to Other Assets, Amount									20,469	22,232	32,147
Solid Capacitors [Member]
Segment and geographic information
Assets	426,751				447,540				426,751	447,540
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property									(536)	(606)	705
Asset Impairment Charges									0	0	3,920
Restructuring charges									1,916	3,297	8,108
Net sales									556,303	621,275	626,494
Operating income (loss)									129,909	135,946	91,848
Depreciation and amortization									21,318	21,202	28,081
Additions to Other Assets, Amount									10,098	12,552	10,498
Film and Electrolytic
Segment and geographic information
Assets	235,493				235,044				235,493	235,044
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property									270	1,008	(767)
Asset Impairment Charges									0	0	556
Restructuring charges									1,714	8,221	5,657
Net sales									178,520	201,917	207,172
Operating income (loss)									(71)	(16,685)	(17,587)
Depreciation and amortization									11,984	13,886	14,557
Additions to Other Assets, Amount									5,902	7,752	14,494
Corporate
Segment and geographic information
Assets	$ 40,300				$ 64,109				40,300	64,109
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property									(109)	(181)	30
Restructuring charges									548	1,499	357
Operating income (loss)									(97,512)	(96,883)	(92,472)
Depreciation and amortization									5,714	5,680	6,889
Additions to Other Assets, Amount									$ 4,469	$ 1,928	$ 7,155