Restructuring - Summary of Restructuring Plans (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Incurred during year		$ 200
Electro-magnetic, Sensors & Actuators [Member] | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Incurred during year		3,300
Corporate | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Total expected to be incurred	$ 2,734	2,734
Incurred during year	2,734	900
Cumulative incurred to date	2,734	2,734
Corporate | Relocation & Exit Costs
Restructuring Cost and Reserve [Line Items]
Total expected to be incurred	909	909
Incurred during year	909
Cumulative incurred to date	909	909
TOKIN | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Total expected to be incurred	4,397	4,397
Incurred during year	4,397
Cumulative incurred to date	4,397	4,397
TOKIN | Relocation & Exit Costs
Restructuring Cost and Reserve [Line Items]
Total expected to be incurred	0	0
Incurred during year	0
Cumulative incurred to date	0	0
Solid Capacitors | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Total expected to be incurred	897	897
Incurred during year	0	100
Cumulative incurred to date	0	0
Solid Capacitors | Relocation & Exit Costs
Restructuring Cost and Reserve [Line Items]
Total expected to be incurred	2,098	2,098
Incurred during year	0
Cumulative incurred to date	0	0
Film and Electrolytic | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Total expected to be incurred	5,243	5,243
Incurred during year	5,243
Cumulative incurred to date	5,243	5,243
Film and Electrolytic | Relocation & Exit Costs
Restructuring Cost and Reserve [Line Items]
Total expected to be incurred	0	0
Incurred during year	0
Cumulative incurred to date	$ 0	$ 0