Share-Based Compensation - 2016 Employee Stock Purchase Plan (Details)		3 Months Ended			9 Months Ended
	May 22, 2018 shares	Sep. 30, 2018 USD ($) employee $ / shares shares	Sep. 30, 2017 $ / shares shares	Jun. 30, 2017 shares	Sep. 30, 2018 USD ($) employee $ / shares shares	Sep. 30, 2017 $ / shares shares	Jan. 01, 2018 shares	Apr. 30, 2016 shares	Apr. 30, 2015 shares
2016 Employee Stock Purchase Plan
Expected stock price volatility			66.50%		66.30%	65.80%
Expected life of options (years)			6 years 1 month 6 days		5 years 9 months 18 days	5 years 10 months 24 days
Expected dividend yield			0.00%		0.00%	0.00%
Risk free interest rate			2.00%		2.70%	2.00%
Number of Options
Vested		135,500		337,500
Number of executives | employee		2			2
Remaining nonvested options				150,000
Forfeited, nonvested		307,121,000	0		422,010,000	3,250,000
Compensation expense, vesting acceleration | $		$ 900,000
Unrecognized share-based compensation
Unrecognized share-based compensation cost | $		4,800,000			$ 4,800,000
Unrecognized share-based compensation - Weighted average period					1 year 8 months 12 days
Restricted stock awards
Unrecognized share-based compensation
Unrecognized share-based compensation cost - RSA | $		$ 0			$ 0
ESPP
2016 Employee Stock Purchase Plan
Granted (in shares)					0
Common stock reserved for issuance (in shares)								150,000
A&R 2015 Plan
2016 Employee Stock Purchase Plan
Granted (in shares)	300,000
Common stock reserved for issuance (in shares)	3,115,077						415,077
Number of Options
Stock options outstanding		2,823,732			2,823,732
Employees, Directors, Officers And Consultants
Number of Options
Vested		279,924
Employees, Directors, Officers And Consultants | A&R 2015 Plan
2016 Employee Stock Purchase Plan
Granted (in shares)		0	65,000		822,000	248,500
Vesting period					4 years
Weighted average fair value per share of options granted | $ / shares		$ 0.00	$ 10.65		$ 5.07	$ 7.35
Employees, Directors And Consultants | A&R 2015 Plan
2016 Employee Stock Purchase Plan
Common stock reserved for issuance (in shares)								2,400,000
Number of Options
Vested					1,693,952
Employees, Directors And Consultants | 2015 Plan
2016 Employee Stock Purchase Plan
Common stock reserved for issuance (in shares)									320,615
Number of Options
Vested			125,115		587,334	713,140
Available for future issuance		678,303			678,303