Stockholders' Equity - Warrants Outstanding Roll Forward (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
MGM Warrant
Number of Shares Outstanding Under Warrants
Warrants outstanding, ending balance	2,667
Warrants
Number of Shares Outstanding Under Warrants
Warrants outstanding, beginning balance	4,267	3,617
Granted	0	1,100
Exercised	0	(450)	(1,191)
Warrants outstanding, ending balance	4,267	4,267	3,617
Weighted Average Exercise Price
Weighted average exercise price, beginning balance	$ 3.61	$ 3.09
Granted	0.00	4.44
Exercised		1.50
Weighted average exercise price, ending balance	$ 3.61	$ 3.61	$ 3.09
Average Contractual Term
Average contractual term	4 years 9 months 11 days	5 years 6 months
Proceeds from exercise of warrants	$ 0	$ 675	$ 2,786