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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 39,092	$ 33,032	$ 121,566	$ 110,352
BASIC:
Weighted Average Number of Shares Outstanding, Basic	41,108,699	39,283,919	40,681,582	38,735,262
DILUTED:
Weighted average common shares outstanding, diluted	41,108,699	39,283,919	40,681,582	38,735,262
Stock options, diluted	74,769	93,437	69,210	49,248
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	264,795	274,544	186,545	91,515
Average dilutive common shares outstanding	41,448,263	39,651,900	40,937,337	38,876,025
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.95	$ 0.84
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.94	$ 0.83	$ 2.97	$ 2.84
Incremental shares excluded since anti-dilutive:
Stock options with an exercise price in excess of the market price for our common shares	403	0	760	8,490
Common Stock, Dividends, Per Share, Declared	$ 0.95	$ 0.90	$ 2.85
Common Stock Dividends, Per Share, Declared, Regular			$ 2.85	$ 2.70