Debt (Textuals) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Long-term debt	$ 228,600,000	$ 298,200,000
Long-term debt, excluding current portion	226,200,000	228,900,000
Interest expense	11,700,000	15,600,000	$ 18,100,000
Aggregate annual maturities of long-term debt [Abstract]
2017	2,400,000
2018	32,600,000
2019	100,000
2020	26,400,000
Thereafter	$ 168,000,000
Senior A Notes Due 2022 [Member]
Line of Credit Facility [Line Items]
Debt instrument, maturity date	Jul. 05, 2022
Debt instrument, stated interest rate	3.67%
Senior B Notes Due 2024 [Member]
Line of Credit Facility [Line Items]
Debt instrument, maturity date	Jul. 05, 2024
Debt instrument, stated interest rate	3.82%
Senior C Notes Due 2027 [Member]
Line of Credit Facility [Line Items]
Debt instrument, maturity date	Jul. 05, 2027
Debt instrument, stated interest rate	4.02%
Euro Note B Due 2016 [Member]
Line of Credit Facility [Line Items]
Long-term debt		66,800,000
Debt Instrument, face amount		61,100,000
Debt instrument, maturity date	Feb. 29, 2016
Debt instrument, stated interest rate	0.00%
Revolving Credit Facility Due 2017 [Member]
Line of Credit Facility [Line Items]
Variable rate basis	LIBOR
Term Loan Due 2018 [Member]
Line of Credit Facility [Line Items]
Long-term debt	$ 34,900,000	37,100,000
Long-term Debt, Current Maturities	2,400,000
Debt issuance costs, net	$ 100,000	100,000
Variable rate basis	LIBOR
Basis spread on variable interest rate	150.00%
Long-term Debt, Gross	$ 34,900,000
Debt Instrument, face amount	$ 42,800,000
Debt Instrument, Term	5 years
Debt instrument, maturity date	Jan. 31, 2018
Debt instrument, stated interest rate	2.27%
Revolving credit facility, due 2020 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, current borrowing capacity	$ 300,000,000.0
Line of Credit Facility, additional borrowing capacity	100,000,000
Credit facility is available for swing-line loans	30,000,000.0
Credit available for the issuance of letters of credit	30,000,000.0
Line of credit, noncurrent	26,400,000	27,100,000
Line of Credit Facility, unused commitment level	270,600,000
Deferred Finance Costs, Own-share Lending Arrangement, Issuance Costs, Adjustment	$ 1,300,000	$ 1,600,000
Debt instrument, maturity date	Oct. 31, 2020
Debt instrument, stated interest rate	1.00%
Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, face amount	$ 168,000,000
Weighted average of the coupon interest rate	3.87%
Annual effective interest rate	4.16%
Deferred Finance Costs, Own-share Lending Arrangement, Issuance Costs, Net, Classification	0.8	0.9
Senior Notes [Member] | Senior A Notes Due 2022 [Member]
Line of Credit Facility [Line Items]
Long-term debt	$ 42,000,000	$ 42,000,000
Debt Instrument, face amount	$ 42,000,000
Debt instrument, stated interest rate	3.67%
Senior Notes [Member] | Senior B Notes Due 2024 [Member]
Line of Credit Facility [Line Items]
Long-term debt	$ 53,000,000	53,000,000
Debt Instrument, face amount	$ 53,000,000
Debt instrument, stated interest rate	3.82%
Senior Notes [Member] | Senior C Notes Due 2027 [Member]
Line of Credit Facility [Line Items]
Long-term debt	$ 73,000,000	$ 73,000,000
Debt Instrument, face amount	$ 73,000,000
Debt instrument, stated interest rate	4.02%
Letter of Credit [Member] | Revolving credit facility, due 2020 [Member]
Line of Credit Facility [Line Items]
Outstanding amount	$ 3,000,000
Minimum [Member] | Base Rate [Member] | Revolving credit facility, due 2020 [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	0.00%
Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Revolving credit facility, due 2020 [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	100.00%
Maximum [Member] | Base Rate [Member] | Revolving credit facility, due 2020 [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	75.00%
Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Revolving credit facility, due 2020 [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	175.00%