Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic Net Income (Loss) Per Share
Net income (loss)	$ (12,484)	$ 34,425	$ (199,567)	$ 58,472
Weighted average common shares outstanding	205,141,000	187,682,000	200,200,000	187,433,000
Basic net income (loss) per share	$ (0.06)	$ 0.18	$ (1.00)	$ 0.31
Diluted Net Income (Loss) Per Share
Diluted net income (loss)	$ (12,484)	$ 34,425	$ (199,567)	$ 58,472
Weighted average common shares outstanding	205,141,000	187,682,000	200,200,000	187,433,000
Dilutive stock options and RSU’s		5,333,000		5,387,000
Weighted average shares used to compute diluted net income (loss) per share	205,141,000	193,015,000	200,200,000	192,820,000
Diluted net income (loss) per share	$ (0.06)	$ 0.18	$ (1.00)	$ 0.30
Anti-dilutive securities
Potential common shares excluded from diluted net loss per share computation	12,603,888	17,276,649	12,603,888	17,230,774
Stock Options
Anti-dilutive securities
Potential common shares excluded from diluted net loss per share computation	12,085,346	2,790,121	12,085,346	2,744,246
0.375% Convertible Senior Notes due 2018
Anti-dilutive securities
Potential common shares excluded from diluted net loss per share computation	149,603	7,245,244	149,603	7,245,244
1.25% Convertible Senior Notes due 2020
Anti-dilutive securities
Potential common shares excluded from diluted net loss per share computation	368,939	7,241,284	368,939	7,241,284