Debt (Details) € in Thousands, ¥ in Millions				1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended	96 Months Ended
	Apr. 28, 2017 USD ($)	Sep. 01, 2016 USD ($) Rate	Sep. 01, 2016 JPY (¥) Rate	Jul. 31, 2017 EUR (€)	Jul. 31, 2017 USD ($)	Jan. 31, 2017 EUR (€)	Jan. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2017 USD ($)	Feb. 01, 2025 EUR (€)	Feb. 01, 2025 USD ($)	Sep. 30, 2017 Rate	Mar. 31, 2017 EUR (€)	Mar. 31, 2017 USD ($)	May 02, 2016 USD ($)	May 05, 2010
Debt, Long-term and Short-term, Combined Amount [Abstract]
Total debt								$ 328,162,000		$ 328,162,000							$ 388,211,000
Revolving line of credit								0		0							33,881,000
Current maturities								(20,359,000)		(20,359,000)							(2,000,000)
Total long-term debt								307,803,000		307,803,000							386,211,000
Interest expense
Contractual interest expense								6,680,000	$ 9,693,000	23,762,000	$ 29,091,000
Capitalized interest								(41,000)	(48,000)	(80,000)	(151,000)
Amortization of debt issuance costs								98,000	348,000	410,000	1,044,000
Amortization of debt (premium) discount								570,000	(204,000)	1,326,000	(603,000)
Imputed interest on acquisition-related obligations								28,000	39,000	84,000	120,000
Interest expense on capital lease								72,000	90,000	230,000	250,000
Total interest expense								7,407,000	$ 9,918,000	25,732,000	$ 29,751,000
Long-term Debt, Unclassified [Abstract]
Second part of loan				€ 277	$ 325,000
Term Loan Credit Agreement [Member]
Debt
Amortization of financing and debt discount										13,800,000		$ 0
Debt, Long-term and Short-term, Combined Amount [Abstract]
Total debt								322,540,000		322,540,000							0
Long-term Debt, Unclassified [Abstract]
Interest payable								200,000		200,000							0
10.5% Senior Notes, net [Member]
Debt
Amortization of financing and debt discount										0		$ (500,000)
Debt, Long-term and Short-term, Combined Amount [Abstract]
Total debt								0		0							352,472,000
Line of Credit Facility [Abstract]
Rate																			10.50%
Long-term Debt, Unclassified [Abstract]
Repayments of debt										353,000,000
Interest payable								0		0							15,400,000
Revolving Credit Facility [Member]
Line of Credit Facility [Abstract]
Current borrowing capacity																		$ 75,000,000
Remaining borrowing capacity								65,100,000		65,100,000
Other Debt Obligations [Member]
Debt
Amortization of financing and debt discount								500,000
Debt, Long-term and Short-term, Combined Amount [Abstract]
Total debt								$ 5,622,000		$ 5,622,000							1,858,000
Long-term Debt, Unclassified [Abstract]
Proceeds from Issuance of Debt						€ 2,200	$ 2,500,000
Debt Instrument, Unamortized Discount																€ 500	$ 600,000
Term Loan Credit Agreement [Member] | Line of Credit [Member]
Debt
Line of Credit Facility, Periodic Payment	$ 4,300,000
Line of Credit, Debt Issue Discount Percent	3.00%
Line of Credit Facility, Maximum Borrowing Capacity	$ 345,000,000
Line of Credit Facility, Maximum Borrowing Capacity, Incremental Increase	$ 50,000,000
Line of Credit, Covenant Compliance, Pledged Percent of Outstanding Voting Stock	65.00%
Line of Credit Facility, Periodic Payment, Percent	1.25%
Line of Credit Facility [Abstract]
Rate	0.97%
Term Loan Credit Agreement [Member] | Line of Credit [Member] | Base Rate [Member]
Line of Credit Facility [Abstract]
Basis spread on variable rate	5.00%
Term Loan Credit Agreement [Member] | Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Abstract]
Basis spread on variable rate	6.00%
Minimum [Member] | Term Loan Credit Agreement [Member] | Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Abstract]
Basis spread on variable rate	1.00%
Scenario, Forecast [Member] | Other Debt Obligations [Member]
Long-term Debt, Unclassified [Abstract]
Long-term Debt, Maturities, Repayment Terms													P8Y	P8Y
TOKIN [Member] | Other Debt Obligations [Member]
Debt
Line of Credit, Debt Issue Discount Percent | Rate		0.04%	0.04%
Line of Credit Facility [Abstract]
Rate | Rate															0.53%
Long-term Debt, Unclassified [Abstract]
Proceeds from Issuance of Debt		$ 3,100,000	¥ 350
Initial Repayment [Member] [Member] | Scenario, Forecast [Member] | Other Debt Obligations [Member]
Long-term Debt, Unclassified [Abstract]
Repayments of Other Debt													€ 185	$ 211,000
Remaining Repayment [Member] | Scenario, Forecast [Member] | Other Debt Obligations [Member]
Long-term Debt, Unclassified [Abstract]
Repayments of Other Debt													€ 210	$ 248,000