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Income Taxes (Schedule Of Additional Information Related To Unrecognized Uncertain Tax Positions) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2012
Income Tax Disclosure [Abstract]        
Gross unrecognized tax benefits on uncertain tax positions (reflected in current income tax and other noncurrent liability accounts in the balance sheet) $ 1,962 $ 3,315 $ 4,049 $ 3,255
Deferred income tax assets related to unrecognized tax benefits on uncertain tax positions (reflected in deferred income tax accounts in the balance sheet) (153) (345) (858)  
Net unrecognized tax benefits on uncertain tax positions, which would impact the effective tax rate if recognized 1,809 2,970 3,191  
Interest and penalties accrued on deductions taken relating to uncertain tax positions (approximately $(1), $(262) and $90 reflected in income tax expense in the income statement in 2017, 2016 and 2015, respectively, with the balance shown in current income tax and other noncurrent liability accounts in the balance sheet) 136 135 397  
Interest and penalties accrued on deductions taken relating to uncertain tax positions, reflected in income tax expense in the income statement (1) (262) 90  
Related deferred income tax assets recognized on interest and penalties (32) (49) (148)  
Interest and penalties accrued on uncertain tax positions net of related deferred income tax benefits, which would impact the effective tax rate if recognized 104 86 249  
Total net unrecognized tax benefits on uncertain tax positions reflected in the balance sheet, which would impact the effective tax rate if recognized $ 1,913 $ 3,056 $ 3,440