Operating Leases - Narrative (Details)	3 Months Ended
	Mar. 31, 2019 USD ($) ft² term	Mar. 31, 2018 USD ($)
Lessee, Lease, Description [Line Items]
Monthly rent	$ 38,202,000	$ 0
Operating lease cost (including related operating costs)	75,000
Short-term lease cost	$ 76,000
Canada
Lessee, Lease, Description [Line Items]
Office space, square foot | ft²	31,100
Lease term	5 years
Renewal option | term	1
Renewal term	5 years
Monthly rent	$ 12,900
Related operating expenses	12,500
Operating lease cost (including related operating costs)	75,000
Rent expense Under ASC 840		81,000
Massachusetts
Lessee, Lease, Description [Line Items]
Rent expense Under ASC 840		26,000
Short-term lease minimum monthly rent	10,000
Short-term lease cost	27,000
Pennsylvania
Lessee, Lease, Description [Line Items]
Rent expense Under ASC 840		$ 24,000
Short-term lease minimum monthly rent	10,000
Short-term lease cost	$ 49,000