Supplemental Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 204,389	$ 201,663	$ 183,020	$ 158,691	$ 137,083	$ 104,554	$ 115,315	$ 114,544	$ 747,763	$ 471,496	$ 676,865
Operating Income (loss)	9,840	9,882	7,968	3,746	(8,198)	(15,055)	(15,135)	(18,825)	31,436	(57,213)	(99,099)
Income (loss) from continuing operations - basic	7,917	2,653	1,632	(983)	(57)	(13,451)	(13,904)	(13,300)	11,219	(40,712)	(90,828)
Net income (loss)	$ (9,450)	$ 2,653	$ 1,632	$ (983)	$ (57)	$ (13,451)	$ (13,904)	$ (13,300)	$ (6,148)	$ (40,712)	$ (90,828)
Income (loss) from continuing operations, basic (in dollars per share)	$ 0.09	$ 0.03	$ 0.02	$ (0.01)	$ 0.00	$ (0.16)	$ (0.17)	$ (0.16)	$ 0.13	$ (0.49)	$ (1.10)
Net income (loss), basic (in dollars per share)	(0.11)	0.03	0.02	(0.01)	0.00	(0.16)	(0.17)	(0.16)	(0.07)	(0.49)	(1.10)
Income (loss) from continuing operations, diluted (in dollars per share)	0.09	0.03	0.02	(0.01)	0.00	(0.16)	(0.17)	(0.16)	0.13	(0.49)	(1.10)
Net income (loss), diluted (in dollars per share)	$ (0.11)	$ 0.03	$ 0.02	$ (0.01)	$ 0.00	$ (0.16)	$ (0.17)	$ (0.16)	$ (0.07)	$ (0.49)	$ (1.10)