Net Income Per Common Share (Schedule 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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic Earnings (Loss) Per Share
Net income available to common shareholders	$ 73,444	$ 57,898	$ 142,742	$ 107,870
Weighted average common shares outstanding (in shares)	122,203	125,100	122,251	126,164
Net income per common share, basic (in dollars per share)	$ 0.60	$ 0.46	$ 1.17	$ 0.85
Diluted Earnings (Loss) Per Share
Net income available to common shareholders	$ 73,444	$ 57,898	$ 142,742	$ 107,870
Weighted average common shares outstanding (in shares)	122,203	125,100	122,251	126,164
Potentially dilutive shares from outstanding equity-based awards (in shares)	824	599	792	614
Weighted average number of diluted common shares (in shares)	123,027	125,699	123,043	126,778
Net income per common share, diluted (in dollars per share)	$ 0.60	$ 0.46	$ 1.16	$ 0.85