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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Basic Earnings (Loss) Per Share
Net income available to common shareholders	$ 108,622	$ 73,444	$ 209,229	$ 142,742
Weighted average common shares outstanding (in shares)	118,397	122,203	118,531	122,251
Net income per common share, basic (in dollars per share)	$ 0.92	$ 0.60	$ 1.77	$ 1.17
Diluted Earnings (Loss) Per Share
Net income available to common shareholders	$ 108,622	$ 73,444	$ 209,229	$ 142,742
Weighted average common shares outstanding (in shares)	118,397	122,203	118,531	122,251
Potentially dilutive shares from outstanding equity-based awards and Earnout Payments (in shares)	742	824	698	792
Weighted average number of diluted common shares (in shares)	119,139	123,027	119,229	123,043
Net income per common share, diluted (in dollars per share)	$ 0.91	$ 0.60	$ 1.75	$ 1.16