Restructuring Charge (Details)	3 Months Ended		6 Months Ended			12 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) ft²	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Restructuring charge
Restructuring charge	$ 699,000	$ 19,342,000	$ 1,524,000		$ 19,901,000
Operating lease right-of-use asset impairment					559,000
Workforce reduction
Restructuring charge
Balance at beginning of the period			4,087,000
Additional charges/adjustments during the period			(116,000)
Payments during the period			(2,242,000)
Balance at end of the period	$ 1,729,000		1,729,000	$ 4,087,000		$ 4,087,000
Workforce reduction | 2019 Corporate Restructuring
Restructuring
Charge for severance related to a pre-existing plan		16,000,000.0
Costs incurred				$ 15,300,000
Incremental retention benefits | 2019 Corporate Restructuring
Restructuring
Costs incurred		$ 4,000,000.0	$ 1,600,000			$ 2,400,000
Winter Street 930 Waltham MA
Restructuring charge
Unoccupied office space for sub-lease | ft²			10,281
Leasehold impairment charge					$ 559,000