Principles Of Preparation (Supplemental Cash Flow Disclosures) (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Supplemental Cash Flow Information [Abstract]
Interest on long-term debt and borrowings under the revolving credit facility	$ 47,871	$ 47,479
Income taxes paid, net	2,567	2,480
Changes in accrued plant additions	1,721	9,347
Right-of-use assets obtained in exchange for lease obligations	5,889	0
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock issued	1,393	1,030
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock issued	$ 2,143	$ 1,499

(Increase) Decrease in capital expenditures incurred but not yet paid

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