Leases - Operating Leases (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) ft² item	Dec. 31, 2018 USD ($)	Mar. 31, 2019 USD ($)	Feb. 29, 2016 ft²
Lessee, Lease, Description [Line Items]
Sub-lease space | ft²	80,000
Excuted sub-lease space | ft²	18,000
Number of real estate leases | item	2
Lease, Practical Expedients, Package [true false]	true
Lessee, Operating Lease, Existence of Option to Extend [true false]	true
Weighted average remaining term of the operating leases	6 years
Right-of-use assets	$ 15,587,000
Lease liabilities	24,769,000
Unamortized lease incentive and straight-line lease liability balances	$ 9,700,000
Weighted-average discount rate	11.00%
Aggregate adjustment to ROU asset	$ 1,000,000
Lease expense for operating lease payments	4,300,000	$ 5,800,000
Cash paid against operating lease liabilities	5,300,000
Operating lease right-of-use asset impairment	$ 694,000
830 Winter Street, Waltham, MA
Lessee, Lease, Description [Line Items]
Number of real estate leases | item	2
Area of Real Estate Property | ft²	120,000
Number of additional terms for which lease agreement can be extended | item	2
Operating lease term extension period	5 years
Winter Street 930 Waltham MA
Lessee, Lease, Description [Line Items]
Area of Real Estate Property | ft²				10,281
Operating lease right-of-use asset impairment	$ 559,000
ASU 2016-2 | Restatement Adjustment
Lessee, Lease, Description [Line Items]
Right-of-use assets			$ 17,600,000
Lease liabilities			$ 27,300,000