Debt And Credit Arrangements Senior Secured Revolving Credit Facility (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Amortization of Debt Issuance Costs	$ 1,279,000	$ 1,284,000	$ 1,290,000
Debt Instrument, Interest Rate, Stated Percentage	2.00%
Borrowings on revolving credit facilities	$ 302,200,000	3,800,000	$ 68,800,000
Senior Secured Revolving Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Term	5 years
Line of Credit Facility, Maximum Borrowing Capacity	$ 450,000,000
Long-term Debt, Gross		$ 0
Senior Secured Revolving Credit Facility, due 2022 [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Term	5 years
Line of Credit Facility, Maximum Borrowing Capacity	$ 450,000,000
Write off of Deferred Debt Issuance Cost	$ 200,000
Line of Credit Facility, Interest Rate Description	Revolving loans under the SSRCF bear interest, at the applicable Borrower’s election, at a rate per annum equal to either (i) the greatest of (a) the Prime Rate (as defined in the SSRCF) in effect on such day, (b) the NYFRB Rate (as defined in the SSRCF) in effect on such day plus 1/2 of 1.0% and (c) the Adjusted LIBOR (as defined in the SSRCF) for a one-month interest period on such day (or if such day is not a business day, the immediately preceding business day) plus 1.0% (the “Adjusted Base Rate”), plus a margin that varies with the Company’s leverage ratio, or (ii) the Adjusted LIBOR (as defined in the SSRCF) for the relevant interest period in effect for day, plus a margin that varies with our leverage ratio.
Debt Instrument, Covenant Description	Significant financial covenants for the SSRCF include a minimum liquidity requirement equal to the principal amount of the 2018 Notes outstanding six months prior to the maturity date of the 2018 Notes and when holders of the 2018 Notes have the option to require us to repurchase the 2018 Notes, a maximum leverage ratio of 3.25 and a minimum interest coverage to EBITDA ratio of 3.0. The required leverage ratio can be relaxed on up to two occasions, upon notification to the lenders, to 3.75 for up to four consecutive fiscal quarters, for acquisitions and plant expansions of $100.0 or greater. The SSRCF contains a number of other customary covenants including, but not limited to, restrictions on our ability to incur additional indebtedness, create liens or other encumbrances, sell assets, enter into sale and lease-back transactions, make certain payments, investments, loans, advances or guarantees, make acquisitions and engage in mergers or consolidations and pay dividends or distributions. At December 31, 2017, we were in compliance with all covenants.
Debt Instrument, Covenant Compliance	At December 31, 2017, we were in compliance with all covenants.
Debt Issuance Costs, Gross	$ 1,600,000
Unamortized Debt Issuance Expense	2,400,000
Amortization of Debt Issuance Costs	600,000
Long-term Debt, Gross	$ 239,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Borrowings on revolving credit facilities	$ 300.0
Interest Expense, Debt	2,700,000
Letters of Credit Outstanding, Amount	42,900,000
Line of Credit Facility, Remaining Borrowing Capacity	$ 168,100,000
Maximum Percentage Of Capital Stock Guaranteed By Company's Material Non-U.S. Subsidiaries For Obligations Under The Senior Credit Facility	65.00%
Senior Secured Revolving Credit Facility, due 2022 [Member] | Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.20%
Line of Credit, Participation Fee Percentage	1.50%
Senior Secured Revolving Credit Facility, due 2022 [Member] | Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.375%
Line of Credit, Participation Fee Percentage	2.50%
Senior Secured Revolving Credit Facility, due 2022 [Member] | Revolving Credit Facility Sub-limit - Swingline [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 25,000,000
Senior Secured Revolving Credit Facility, due 2022 [Member] | Revolving Credit Facility Sub-limit - Letters of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100,000,000
Senior Secured Revolving Credit Facility, due 2022 [Member] | Revolving Credit Facility Sub-limit - Foreign Currency [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100,000,000
Senior Secured Revolving Credit Facility, due 2022 [Member] | Revolving Credit Facility Sub-limit - Foreign Borrower [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100,000,000
Senior Secured Revolving Credit Facility, due 2022 [Member] | Revolving Credit Facility Sub-limit - Expansion Option [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 225,000,000
Revolving Credit Facility [Member] | Senior Secured Revolving Credit Facility, due 2022 [Member]
Debt Instrument [Line Items]
Fronting Fee Percentage Charged For Issuance Of Letters Of Credit	0.125%