Earnings Per Share (Weighted-Average Shares of Common Stock Outstanding Used in Calculation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net (loss) income	$ (15,370)	$ (155,946)	$ 70,976	$ (206,673)
Basic weighted-average shares outstanding	124,604	127,170	125,041	128,397
Dilutive impact of stock options and restricted shares			720
Diluted weighted-average shares outstanding	124,604	127,170	125,761	128,397
Net (loss) income per common share:
Basic	$ (0.12)	$ (1.23)	$ 0.57	$ (1.61)
Diluted	$ (0.12)	$ (1.23)	$ 0.56	$ (1.61)