Earnings and Dividends Per Share (Summary Of Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 38,245		$ 44,595	$ 82,475	$ 77,320
BASIC:
Weighted Average Number of Shares Outstanding, Basic	40,982,244		38,520,221	40,468,024	38,460,934
DILUTED:
Weighted average common shares outstanding, diluted	40,982,244		38,520,221	40,468,024	38,460,934
Stock options, diluted	66,137		41,163	63,901	27,154
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	196,792	147,420	0	147,420	0
Average dilutive common shares outstanding	41,245,173		38,561,384	40,679,345	38,488,088
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.93		$ 1.16
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.93		$ 1.16	$ 2.03	$ 2.01
Incremental shares excluded since anti-dilutive:
Stock options with an exercise price in excess of the market price for our common shares	11,015		14,940	9,736	41,773
Common Stock, Dividends, Per Share, Declared	$ 0.95		$ 0.90	$ 1.90
Common Stock Dividends, Per Share, Declared, Regular				$ 1.90	$ 1.80