Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accounting Policies [Abstract]
Discount rate, present value of future revenue			10.00%
Impairment charges	$ 0	$ 0	$ 0	$ 158,633
Capitalized general and administrative costs	6,100	4,300	16,900	10,300
Interest costs capitalized	$ 2,100	$ 700	$ 5,200	$ 2,900