Earnings Per Common Share (Summary Of Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Common Share [Abstract]
Net income used for basic and diluted calculation	$ 94,338	$ (183,757)	$ 306,564	$ 77,781
Shares used in computing earnings per common share—basic	224,180	226,228	224,454	209,373
Stock awards	1,908	0	2,106	2,435
Shares used in computing earnings per common share-diluted	226,088	226,228	226,560	211,808
Earnings Per Share, Basic	$ 0.42	$ (0.81)	$ 1.37	$ 0.37
Earnings Per Share, Diluted	$ 0.42	$ (0.81)	$ 1.35	$ 0.37