Summary of Significant Accounting Policies (Details 1) - 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
Basic earnings (loss) per share computation:
Net income (loss) attributable to common stockholders —basic	$ (6,121)	$ (8,982)	$ (919)	$ 831	$ (5,431)	$ (2,703)	$ (2,901)	$ (950)	$ (15,191)	$ (11,985)	$ 6,668
Weighted average common shares —basic (in shares)									53,323,954	53,078,158	52,872,814
Basic (loss) earnings per share (in dollars per share)	$ (0.11)	$ (0.17)	$ (0.02)	$ 0.02	$ (0.11)	$ (0.05)	$ (0.05)	$ (0.02)	$ (0.28)	$ (0.23)	$ 0.13
Dilutive earnings (loss) per share computation:
Net income (loss) attributable to common stockholders —basic	$ (6,121)	$ (8,982)	$ (919)	$ 831	$ (5,431)	$ (2,703)	$ (2,901)	$ (950)	$ (15,191)	$ (11,985)	$ 6,668
Interest expense related to convertible 3.75% senior notes									0	0	5,391
Amortization of discount related to convertible 3.75% senior notes									0	0	6,680
Change in the fair value of derivative									0	0	(23,144)
Net loss attributable to common stockholders —diluted									$ (15,191)	$ (11,985)	$ (4,405)
Share Computation:
Weighted average common shares —basic (in shares)									53,323,954	53,078,158	52,872,814
Effect of convertible 3.75% senior notes (in shares)									0	0	12,732,168
Effect of dilutive stock options and warrants (in shares)									0	0	1,507,013
Weighted average common shares outstanding —diluted (in shares)									53,323,954	53,078,158	67,111,995
Diluted (loss) earnings per share (in dollars per share)	$ (0.11)	$ (0.17)	$ (0.02)	$ 0.02	$ (0.11)	$ (0.05)	$ (0.05)	$ (0.02)	$ (0.28)	$ (0.23)	$ (0.07)
Convertible debt
Share Computation:
Stated interest rate	3.75%				3.75%				3.75%	3.75%	3.75%