Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share ) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Net income		$ 20,888	$ 43,600	$ 63,985	$ 90,983
Average shares used in basic computation		68,370	66,302	68,189	66,167
Dilutive effect of stock options and units	[1]	9,486	9,339	9,435	9,498
Average shares used in diluted computation		77,856	75,641	77,624	75,665
Earnings per common share: Basic		$ 0.31	$ 0.66	$ 0.94	$ 1.38
Earnings per common share: Diluted		$ 0.27	$ 0.58	$ 0.82	$ 1.20

[1] Diluted earnings per share is computed on the basis of the weighted-average number of shares of common stock plus the effect of dilutive potential common shares outstanding during the period using the treasury stock method. Diluted earnings per share include stock options and units.