Earnings Per Share (Comparison Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Basic earnings per share:
Net income	$ 9,458	$ 151,863	$ 133,814	$ 328,835
Weighted average common shares outstanding	92,441,730	97,809,639	94,178,989	98,672,618
Basic earnings per share	$ 0.10	$ 1.55	$ 1.42	$ 3.33
Diluted earnings per share:
Net income	$ 9,458	$ 151,863	$ 133,814	$ 328,835
Weighted average common shares outstanding	92,441,730	97,809,639	94,178,989	98,672,618
Share equivalents:
Warrants and options	1,075,735	1,448,071	1,102,252	1,456,439
RSUs and LTIP awards	452,938	455,744	534,653	550,224
Employee share purchase plan	13,823	11,348	14,561	12,287
Weighted average common shares and common share equivalents outstanding - diluted	93,984,226	99,724,802	95,830,455	100,691,568
Diluted earnings per share	$ 0.10	$ 1.52	$ 1.40	$ 3.27