Organization and Description of Business - Series A Perpetual Convertible Preferred Stock (Details) - $ / shares					9 Months Ended
	Jul. 13, 2017	Apr. 17, 2017	Jan. 19, 2017	Aug. 25, 2016	Sep. 30, 2017	Dec. 31, 2016
Series A Perpetual Convertible Preferred Stock
Series A preferred stock, par value (in dollars per share)					$ 0.001	$ 0.001
Low
Series A Perpetual Convertible Preferred Stock
Number of series of preferred stock authorized					1
Series A preferred stock
Series A Perpetual Convertible Preferred Stock
Shares issued (in shares)				1,840,000
Dividend rate (as a percent)	8.00%	8.00%	8.00%	8.00%
Series A preferred stock, par value (in dollars per share)				$ 0.001
Preferred stock, share price (in dollars per share)				$ 50