Earnings Per Share (Comparison Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share, Basic [Abstract]
Net income	$ (51,630)	$ 30,915	$ 82,184	$ 359,750
Weighted average common shares outstanding	90,882,511	96,458,231	93,068,088	97,926,378
Basic (loss) earnings per share	$ (0.57)	$ 0.32	$ 0.88	$ 3.67
Earnings Per Share, Diluted [Abstract]
Net income	$ (51,630)	$ 30,915	$ 82,184	$ 359,750
Weighted average common shares outstanding	90,882,511	96,458,231	93,068,088	97,926,378
Share equivalents:
Warrants and options	0	1,430,243	1,071,569	1,449,641
RSUs and LTIP awards	0	541,711	569,276	575,675
Employee share purchase plan	0	14,053	16,047	13,602
Weighted average common shares and common share equivalents outstanding - diluted	90,882,511	98,444,238	94,724,980	99,965,296
Diluted (loss) earnings per share	$ (0.57)	$ 0.31	$ 0.87	$ 3.60