Interim Consolidated Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interim Consolidated Financial Information (Unaudited)
Revenues	$ 243,881	$ 187,611	$ 162,984	$ 159,275	$ 123,973	$ 198,147	$ 99,582	$ 89,792	$ 753,751	$ 511,495	$ 354,947
Net income (loss)	$ 55,178	$ (39,582)	$ 9,294	$ (18,359)	$ (36,944)	$ 59,293	$ (36,873)	$ (33,957)	$ 6,531	$ (48,481)	$ (83,147)
Basic net income (loss) per share	$ 0.30	$ (0.22)	$ 0.05	$ (0.11)	$ (0.22)	$ 0.35	$ (0.22)	$ (0.21)	$ 0.04	$ (0.29)	$ (0.56)
Diluted net income (loss) per share	$ 0.29	$ (0.22)	$ 0.05	$ (0.11)	$ (0.22)	$ 0.33	$ (0.22)	$ (0.21)	$ 0.03	$ (0.29)	$ (0.56)
Shares used in computation of basic net income (loss) per share	186,269	181,387	178,676	172,070	169,924	168,592	167,914	165,357	179,601	167,947	148,403
Shares used in computation of diluted net income (loss) per share	193,367	181,387	186,493	172,070	169,924	189,046	167,914	165,357	187,302	167,947	148,403