Organization and Significant Accounting Policies - Option Valuation Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward option fair value, beginning balance	$ (9,900)
Change in value of TOKIN options	0	$ 10,700	$ (26,300)
Forward option fair value, ending balance	0	(9,900)
NEC TOKIN Corporation | Put Option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward option fair value, beginning balance	(9,900)
Forward option fair value, ending balance		(9,900)
Recurring | NEC TOKIN Corporation | Level 3 | Put Option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in value of TOKIN options	9,900	10,700	(26,300)
Other Noncurrent Assets | Recurring | NEC TOKIN Corporation | Level 3 | Put Option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward option fair value, beginning balance	(9,900)	(20,600)
Forward option fair value, ending balance	$ 0	$ (9,900)	$ (20,600)