Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income (loss)	$ (56,700)	$ (59,763)	$ (108,324)	$ (58,993)	$ 24,000	$ 60,265	$ (75,192)	$ (78,909)	$ (283,780)	$ (69,836)	$ 279,370
Less: Basic income allocable to participating securities											(3,286)
Basic net income (loss) allocable to common shareholders									(283,780)	(69,836)	276,084
Diluted adjustments to income allocable to participating securities											58
Diluted net income (loss) allocable to common shareholders									$ (283,780)	$ (69,836)	$ 276,142
Weighted average number of shares used to compute net income (loss) per share:
Basic (in shares)									385,402	382,610	379,195
Restricted stock awards and units (in shares)											6,924
Diluted (in shares)									385,402	382,610	386,119
Net income (loss) per share:
Basic (in dollars per share)	$ (0.15)	$ (0.15)	$ (0.28)	$ (0.15)	$ 0.06	$ 0.16	$ (0.20)	$ (0.21)	$ (0.74)	$ (0.18)	$ 0.73
Diluted (in dollars per share)	$ (0.15)	$ (0.15)	$ (0.28)	$ (0.15)	$ 0.06	$ 0.15	$ (0.20)	$ (0.21)	$ (0.74)	$ (0.18)	$ 0.72
Outstanding restricted stock awards and units excluded from the computations of diluted net income per share (in shares)									11,800	11,200	4,400