Earnings Per Common Share (Computation Of Basic And Diluted Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Earnings Per Share [Abstract]
Net (loss) income	$ (1,851,947)	$ 83,750	$ 84,502	$ 111,810	$ 74,033
Weighted average number of common shares outstanding - basic (in shares)	220,216				220,366
Effect of potentially dilutive common shares (in shares)	0				289
Weighted average number of shares outstanding, diluted (in shares)	220,216				220,655
(LOSS) EARNINGS PER COMMON SHARE:
Basic (in dollars per share)	$ (8.41)				$ 0.34
Diluted (in dollars per share)	$ (8.41)				$ 0.34