Segment and Geographic Information - Net Sales by Country (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
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales	$ 197,519	$ 188,029	$ 187,308	$ 184,935	$ 183,926	$ 177,184	$ 186,123	$ 187,590	$ 757,791	$ 734,823	$ 823,192
Property, plant and equipment, net	209,311				241,839				209,311	241,839
Solid Capacitors
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									575,110	556,303	621,275
Film and Electrolytic
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									$ 182,681	178,520	201,917
Net sales | Film and Electrolytic
Net sales and property, plant and equipment, goodwill, intangible assets
Concentration Risk, Customer									0
Net sales | Sales risk
Net sales and property, plant and equipment, goodwill, intangible assets
Concentration Risk, Customer									1
Concentration Risk, Geographic									No
Net sales									$ 104,400	99,300	124,400
Net sales | Sales risk | Solid Capacitors
Net sales and property, plant and equipment, goodwill, intangible assets
Concentration Risk, Customer									1
Net sales									$ 89,400	85,300	109,100
Net sales | Sales risk | Film and Electrolytic
Net sales and property, plant and equipment, goodwill, intangible assets
Concentration Risk, Customer									1
Net sales										14,000	15,300
Net sales | Geographic risk
Net sales and property, plant and equipment, goodwill, intangible assets
Threshold for Disclosure Percentage									3.00%
Property, Plant and Equipment [Member] | Geographic risk
Net sales and property, plant and equipment, goodwill, intangible assets
Threshold for Disclosure Percentage									3.20749%
United States
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									$ 198,250	201,878	238,840
Property, plant and equipment, net	46,387				54,658				46,387	54,658
Hong Kong
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									121,813	133,117	131,109
Germany
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									104,755	83,589	107,859
Europe [Member]
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									64,316	57,362	58,879
China
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									71,223	65,043	65,289
Property, plant and equipment, net	23,780				26,705				23,780	26,705
Asia Pacific [Member]
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									54,767	61,414	62,864
United Kingdom
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									33,837	28,083	32,127
Netherlands
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									32,478	31,218	38,853
Singapore
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									15,565	16,260	22,516
Italy
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									15,376	14,391	19,013
Property, plant and equipment, net	36,108				44,699				36,108	44,699
Hungary
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									18,856	17,766	22,745
Mexico
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									22,424	23,041	21,164
Property, plant and equipment, net	55,878				61,859				55,878	61,859
Other (1)
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									4,131	1,661	1,934
Property, plant and equipment, net	7,331				9,462				7,331	9,462
PORTUGAL
Net sales and property, plant and equipment, goodwill, intangible assets
Property, plant and equipment, net	21,637				23,449				21,637	23,449
MACEDONIA, THE FORMER YUGOSLAV REPUBLIC OF
Net sales and property, plant and equipment, goodwill, intangible assets
Property, plant and equipment, net	12,339				14,131				12,339	14,131
SWEDEN
Net sales and property, plant and equipment, goodwill, intangible assets
Property, plant and equipment, net	5,851				6,876				5,851	6,876
Non-US [Member]
Net sales and property, plant and equipment, goodwill, intangible assets
Net sales									559,541	532,945	$ 584,352
Property, plant and equipment, net	$ 162,924				$ 187,181				$ 162,924	$ 187,181
Minimum | Net sales | Sales risk
Net sales and property, plant and equipment, goodwill, intangible assets
Concentration risk, percentage									0.00%
Minimum | Net sales | Sales risk | Solid Capacitors
Net sales and property, plant and equipment, goodwill, intangible assets
Concentration risk, percentage									0.00%
Minimum | Net sales | Sales risk | Film and Electrolytic
Net sales and property, plant and equipment, goodwill, intangible assets
Concentration risk, percentage									0.00%