Income Taxes (Schedule Of Additional Information Related To Unrecognized Uncertain Tax Positions) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits on uncertain tax positions (reflected in current income tax, other noncurrent liability accounts, or deferred tax assets in the balance sheet)	$ 628	$ 881	$ 3,361	$ 1,962
Deferred income tax assets related to unrecognized tax benefits on uncertain tax positions (reflected in deferred income tax accounts in the balance sheet)	(110)	(163)	(211)
Net unrecognized tax benefits on uncertain tax positions, which would impact the effective tax rate if recognized	518	718	3,150
Interest and penalties accrued on deductions taken relating to uncertain tax positions (approximately $2, $(144) and $107 reflected in income tax expense in the income statement in 2020, 2019 and 2018, respectively, with the balance shown in current income tax and other noncurrent liability accounts in the balance sheet)	102	100	243
Interest and penalties accrued on deductions taken relating to uncertain tax positions, reflected in income tax expense in the income statement	2	(144)	107
Related deferred income tax assets recognized on interest and penalties	(24)	(23)	(56)
Interest and penalties accrued on uncertain tax positions net of related deferred income tax benefits, which would impact the effective tax rate if recognized	78	77	187
Total net unrecognized tax benefits on uncertain tax positions reflected in the balance sheet, which would impact the effective tax rate if recognized	$ 596	$ 795	$ 3,337