Earnings Per Common Share (Computation Of Basic And Diluted Earnings (Loss) Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net income	$ 111,810	$ 74,033	$ 80,311	$ 90,981	$ 65,999	$ 78,972	$ 185,843	$ 144,971
Weighted average number of common shares outstanding - basic (in shares)	220,487				220,283		220,427	220,326
Effect of potentially dilutive common shares (in shares)	232				364		265	434
Weighted average number of common shares outstanding - diluted (in shares)	220,719				220,647		220,692	220,760
EARNINGS PER COMMON SHARE:
Basic (in usd per share)	$ 0.51				$ 0.30		$ 0.84	$ 0.66
Diluted (in usd per share)	$ 0.51				$ 0.30		$ 0.84	$ 0.66