Restructuring - Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Reconciliation of restructuring liability
Costs charged to expense	$ 14,843	$ 5,404	$ 4,178
Personnel reduction costs
Reconciliation of restructuring liability
Balance at the beginning of the period	$ 999	976	7,239
TOKIN opening balance	0
Costs charged to expense	$ 12,587	2,214	1,803
Costs paid or settled	(3,901)	(2,130)	(8,273)
Change in foreign exchange	147	(61)	207
Balance at the end of the period	9,629	999	976
Personnel reduction costs
Reconciliation of restructuring liability
Costs charged to expense	12,384
Manufacturing and sales office relocation costs
Reconciliation of restructuring liability
Balance at the beginning of the period	$ 406	0	0
TOKIN opening balance	312
Costs charged to expense	$ 2,256	3,190	2,375
Costs paid or settled	(2,662)	(2,784)	(2,375)
Change in foreign exchange	18	0	0
Balance at the end of the period	330	406	0
Employee Relocation
Reconciliation of restructuring liability
Costs charged to expense	200
Film and Electrolytic
Reconciliation of restructuring liability
Costs charged to expense	5,788	3,738	$ 1,714
Film and Electrolytic | Manufacturing and sales office relocation costs
Reconciliation of restructuring liability
Costs charged to expense		$ 600