Impairment charges (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2016	Jun. 30, 2017
Property, Plant and Equipment [Line Items]
Write down of long-lived assets	$ 6.2
Film and Electrolytic [Member]
Property, Plant and Equipment [Line Items]
Write down of long-lived assets	4.1
Impairment of long-lived assets to be disposed of	3.0
Impairment of Intangible assets	1.1
Solid Capacitors
Property, Plant and Equipment [Line Items]
Write down of long-lived assets	$ 2.1
Solid Capacitors | Facility Closing [Member]
Property, Plant and Equipment [Line Items]
Restructuring and Related Cost, Cost Incurred to Date		$ 0.1
Restructuring and related cost, expected cost remaining		$ 1.1