Long-Term Debt And Other Long-Term Liabilities (Long-Term Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Long-term debt and other long-term liabilites [Abstract]
Credit agreement with average interest rates of 3.4% and 2.8% at December 31, 2017 and 2016, respectively	$ 178,000	$ 160,800
6.625% senior subordinated notes due 2021	650,000	650,000
Total principal amount	828,000	810,800
Less: unamortized discount	(2,234)	(2,804)
Less: debt issuance costs, net	(5,490)	(7,079)
Total long-term debt	$ 820,276	$ 800,917
Line of Credit Facility, Interest Rate at Period End	3.40%	2.80%