Financial Instruments (Estimated Fair Values Of Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and short-term investments, Carrying Amount	$ 83,168	$ 57,837
Cash and short-term investments, Fair Value	83,168	57,837
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including current installments on long-term debt and fair value adjustments related to fair value hedges, Carrying Amount	320,003	320,092
Long-term debt, including current installments on long-term debt and fair value adjustments related to fair value hedges, Fair Value	351,712	347,869
Level 2 [Member] | Interest rate contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative asset related to interest rate swaps, Carrying Amount	1,597	1,830
Derivative asset related to interest rate swaps, Fair Value	$ 1,597	$ 1,830