The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Goodwill, Gross	$ 41,386		$ 41,386		$ 41,386
Goodwill, Impaired, Accumulated Impairment Loss	(1,092)		(1,092)		(1,092)
Finite-Lived Intangible Assets, Accumulated Amortization	23,014		23,014		16,953
Intangible Assets, Gross (Excluding Goodwill)	84,082		84,082		46,734
Indefinite-Lived Trademarks	15,024		15,024		7,207
Intangible Assets, Net (Excluding Goodwill)	61,068		61,068		29,781
Goodwill	40,294		40,294		40,294
Amortization of Intangible Assets	1,100	$ 500	3,400	$ 1,600
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	4,600		4,600
Corporate, Non-Segment [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill, Gross	4,710		4,710		4,710
Goodwill, Impaired, Accumulated Impairment Loss	0		0		0
Goodwill	4,710		4,710		4,710
Solid Capacitors [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill, Gross	35,584		35,584		35,584
Goodwill, Impaired, Accumulated Impairment Loss	0		0		0
Goodwill	35,584		35,584		35,584
Film and Electrolytic [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill, Gross	1,092		1,092		1,092
Goodwill, Impaired, Accumulated Impairment Loss	(1,092)		(1,092)		(1,092)
Goodwill	0		0		0
Electro-magnetic, Sensors & Actuators [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	0		0
Purchased technology, customer relationships and patents (2 - 21 years)
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	69,058		69,058		39,527
Finite-Lived Intangible Assets, Accumulated Amortization	23,014		23,014		16,953
Intangible Assets, Net (Excluding Goodwill)	$ 46,044		46,044		22,574
Purchased technology, customer relationships and patents (2 - 21 years) \| Weighted Average [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	14 years 1 month 6 days	16 years 8 months
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Net (Excluding Goodwill)	$ 15,024		$ 15,024		$ 7,207