Income Taxes (Summary Of Deferred Income Tax Asset Valuation Allowance) (Details) - Deferred Income Tax Asset Allowance [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance at beginning of year	$ 109,913	$ 107,312
Additions (reductions) charged to expense	(28,071)	20,450	107,312
Other, deductions	(1,046)	(17,849)
Balance at end of year	$ 80,796	$ 109,913	$ 107,312