Financial Instruments (Estimated Fair Values Of Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and short-term investments, Carrying Amount	$ 50,451	$ 80,062
Cash and short-term investments, Fair Value	50,451	80,062
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including current installments of long-term debt (including fair value adjustments related to fair value hedges), Carrying Amount	320,131	357,576
Long-term debt, including current installments on long-term debt (including fair value adjustments related to fair value hedges), Fair Value	354,445	379,048
Level 2 [Member] | Interest rate contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net derivative asset related to interest rate swaps, Carrying Amount	2,012	2,952
Net derivative asset related to interest rate swaps, Fair Value	$ 2,012	$ 2,952