Stockholders' Equity - Stock Options and Warrants (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($) $ / shares $ / warrant shares	Dec. 31, 2017	Dec. 31, 2018 USD ($)
Warrants, Number of Shares [Roll Forward]
Warrants, Shares, Beginning of Period	30,000
Warrants Granted	0
Warrants Exercised	0
Warrants Canceled	0
Warrants Expired	0
Warrants, Shares, End of Period	30,000
Warrants Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, Warrants Outstanding, Beginning of Period | $ / warrant	5.89
Weighted Average Exercise Price, Warrants Granted | $ / shares	$ 0.00
Weighted Average Exercise Price, Warrants Exercised | $ / shares	0.00
Weighted Average Exercise Price, Warrants Canceled | $ / shares	0.00
Weighted Average Exercise Price, Warrants Expired | $ / shares	$ 0.00
Weighted Average Exercise Price, Warrants Outstanding, End of Period | $ / warrant	5.89
Weighted Average Remaining Contractual Term, Warrant outstanding	3 years 11 months 12 days	4 years 2 months 9 days
Aggregate Intrinsic Value, Warrants Outstanding | $	$ 0		$ 0
Warrants, vested and expected to vest	30,000
Weighted Average Exercise Price, Warrants vested & expected to vest | $ / warrant	5.89
Weighted Average Remaining Contractual Term, Warrants Vested and Expect to Vest	3 years 11 months 12 days
Aggregate Intrinsic Value, Warrants vested and expected to vest | $	$ 0
Warrants, Vested. Number	30,000
Warrants, Vested, Weighted Average Exercise Price | $ / warrant	5.89
Warrants, Vested, Weighted Average Remaining Contractual Term	3 years 11 months 12 days
Warrants, Vested, Aggregate Intrinsic Value | $	$ 0
US Equity Plan [Member]
Options, Outstanding [Roll Forward]
Options, Outstanding, Beginning of Period	1,018,530
Options, Grants in Period, Net of Forfeitures	199,346
Options, Exercises in Period	(240)
Options, Forfeitures in Period	0
Options, Expirations in Period	(4,002)
Options, Outstanding, End of Period	1,213,634
Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options, Outstanding, Weighted Average Exercise Price, Beginning of Period | $ / shares	$ 30.50
Options, Grants in Period, Weighted Average Exercise Price | $ / shares	4.90
Options, Exercises in Period, Weighted Average Exercise Price | $ / shares	3.50
Options, Forfeitures in Period, Weighted Average Exercise Price | $ / shares	0.00
Options, Expirations in Period, Weighted Average Exercise Price | $ / shares	8.30
Options, Outstanding, Weighted Average Exercise Price, End of Period | $ / shares	$ 26.40
Options, Outstanding, Weighted Average Remaining Contractual Term	5 years 10 months 6 days	5 years 3 months 18 days
Options, Outstanding, Intrinsic Value | $	$ 12,900		$ 3,300
Options, Vested and Expected to Vest, Outstanding, Number	1,185,882
Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price | $ / shares	$ 26.90
Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	5 years 9 months 4 days
Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value | $	$ 12,900
Options, Vested and Expected to Vest, Exercisable, Number	974,249
Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price | $ / shares	$ 31.80
Options, Vested, Weighted Average Remaining Contractual Term	4 years 11 months 16 days
Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value | $	$ 12,900