Warrant Transactions - Additional Information (Details) - $ / shares	1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2017	May 31, 2017	Jun. 30, 2018	Dec. 31, 2017	Mar. 31, 2016
Class of Warrant or Right [Line Items]
Warrants issued during the period (in shares)					1,000,000
Warrants exercised (in shares)			0	675,000
Warrants outstanding (in shares)			0	0
Allen F. Stephen Series 2 and 3
Class of Warrant or Right [Line Items]
Warrants exercised (in shares)		425,000
Exercise price of warrants (in dollars per share)		$ 3.55
Issuance of common stock (in shares)		425,000
OTA LLC Series 2
Class of Warrant or Right [Line Items]
Warrants exercised (in shares)	250,000
Exercise price of warrants (in dollars per share)	$ 3.55
Issuance of common stock (in shares)	250,000