Stockholders' Equity - Summary of Warrant Activity (Details)	12 Months Ended
	Dec. 31, 2017 $ / shares shares	Dec. 31, 2016 $ / shares shares	Dec. 31, 2015 $ / shares shares
Warrants Outstanding
Beginning balance (in shares) | shares	6,750	14,250	969,549
Warrants exercised (in shares) | shares			(638,189)
Warrants expired (in shares) | shares			(205,000)
Warrants canceled/forfeited (in shares) | shares	(6,750)	(7,500)	(112,110)
Ending balance (in shares) | shares	0	6,750	14,250
Weighted Average Exercise Price During Period
Beginning balance (in dollars per share) | $ / shares	4.30	4.30	4.61
Warrants exercised (in dollars per share) | $ / shares			4.58
Warrants expired (in dollars per share) | $ / shares			4.20
Warrants canceled/forfeited (in dollars per share) | $ / shares	4.30	4.30	5.54
Ending balance (in dollars per share) | $ / shares	0.00	4.30	4.30