Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Basic EPS
Net income (loss)	$ 69,557	$ (14,219)	$ 63,660	$ (64,185)
Weighted average shares
Basic (in shares)	161,039,000	135,247,000	155,108,000	124,478,000
Effect of stock-based compensation plans (in shares)	4,789,000	0	3,284,000	0
Diluted (in shares)	165,828,000	135,247,000	158,392,000	124,478,000
Income (loss) per share
Basic (in dollars per share)	$ 0.43	$ (0.11)	$ 0.41	$ (0.52)
Diluted (in dollars per share)	$ 0.42	$ (0.11)	$ 0.40	$ (0.52)
Convertible Senior Notes Due March 2028 [Member]
Earnings Per Share (Textual) [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.25%		3.25%		3.25%
Stock Options [Member]
Earnings Per Share (Textual) [Abstract]
Number of shares of common stock equivalents related to convertible debt	215,298	3,302,701	404,543	3,251,347,000,000