Impairment charges (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Disposal Group, Not (Gain) loss on write down and disposal of long-lived assetsDiscontinued Operation, Loss (Gain) on Write-down	$ (902)	$ 132	$ (922)	$ 6,500
Property, Plant and Equipment, Disposals			300
Impairment of long-lived assets to be disposed of			6,200
Film and Electrolytic [Member]
Property, Plant and Equipment [Line Items]
(Gain) loss on write down and disposal of long-lived assets			4,100
Impairment of long-lived assets to be disposed of			3,000
Impairment of Intangible assets			1,100
Solid Capacitors
Property, Plant and Equipment [Line Items]
(Gain) loss on write down and disposal of long-lived assets			$ 2,100