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
Net Income (Loss) (Numerator)
Basic earnings per share - net income (in dollars)	$ 157,397	$ 60,617	$ 362,103	$ 122,928
Diluted earnings per share - net income (in dollars)	$ 157,397	$ 60,617	$ 362,103	$ 122,928
Weighted average common shares outstanding (in shares)
Weighted average common shares outstanding - basic (in shares)	243,761	242,074	243,539	241,836
Dilutive common share equivalents (in shares)	1,921	1,748	1,688	1,557
Weighted average common shares outstanding - diluted (in shares)	245,682	243,822	245,227	243,393
Per Share Amount
Basic (in dollars per share)	$ 0.65	$ 0.25	$ 1.49	$ 0.51
Diluted (in dollars per share)	$ 0.64	$ 0.25	$ 1.48	$ 0.51