Subsequent event (Details) - USD ($)	3 Months Ended	9 Months Ended		45 Months Ended
	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Oct. 26, 2017	Feb. 02, 2017	Dec. 31, 2016	Jan. 28, 2016
Subsequent events
Common stock repurchased (in shares)		0		6,500,000
Credit Facility repaid		$ 9,916,000	$ 4,000,000
Repayments of Lines of Credit		$ 9,916,000	$ 4,000,000
Series A Preferred Stock price per share		$ 0.01		$ 0.01			$ 0.01
Revolving Credit Facility
Subsequent events
Credit Facility borrowed							$ 9,900,000
Credit Facility repaid	$ 9,900,000
Repayments of Lines of Credit	$ 9,900,000
Maximum borrowing capacity						$ 30,000,000		$ 20,000,000
Subsequent event
Subsequent events
Termination fee					$ 7,700,000
Conversion ratio of common stock per share of Series A Preferred Stock					3.05
Common stock offer price					$ 4.50
Series A Preferred Stock price per share					$ 13.725