Supplementary Quarterly Financial Information (Unaudited) - (Details) - USD ($) $ / shares in Units, $ 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
Supplemental Quarterly Financial Information (Unaudited)
Revenues and other income	$ 210,917	$ 66,629	$ 45,676	$ 62,133	$ 121,868	$ 95,318	$ 121,813	$ 132,557	$ 385,355	$ 471,556	$ 882,738
Costs and expenses	268,337	118,890	169,544	123,148	55,903	(27,165)	171,615	185,767	679,919	386,120	304,470
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
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