Restructuring Costs (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		$ 0	$ 4,359	$ 2,389
HUNGARY
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ 3,700		$ 4,400
ZAMBIA
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs				$ 2,400