Recently Adopted Accounting Pronouncement (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue	$ 0	$ 6,924,353
ASU 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Reimbursement agreement	$ 200,000	300,000
ASU 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract liability		3,200,000
ASU 2014-09 [Member] | Accumulated Deficit [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect adjustment		$ 6,700,000