Leases - Additional Information (Details) $ in Thousands	1 Months Ended			12 Months Ended
	Apr. 30, 2019 USD ($) ft²	Aug. 30, 2018	May 31, 2018 USD ($)	Dec. 31, 2019 USD ($) contract renewal_option offering_period	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Oct. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Initial annual base rent	$ 1,900		$ 2,000
Initial annual base rent increase	$ 18,200		22,400
Amounts capitalized under build-to-suit lease transaction				$ 0	$ 11,885	$ 0
Rent expense					1,100	$ 600
Additional office space | ft²	38,003
Operating lease area | ft²	82,346
Operating lease assets				21,158	0
Total operating lease liabilities				$ 17,651				$ 11,900
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Operating lease assets							$ 21,200	800
Total operating lease liabilities							$ 17,000	$ 800
Massachusetts
Lessee, Lease, Description [Line Items]
Lease renewal term				5 years
Remainder of lease extension term				6 months
Sublease term		9 months		3 years
Number of lease options | renewal_option				2
Kansas
Lessee, Lease, Description [Line Items]
Number of lease agreement | contract				2
Term of lease agreements				5 years
Number of additional lease agreements | offering_period				3
Certificates of deposit | Letter of Credit
Lessee, Lease, Description [Line Items]
Cash balance held to secure letter of credit associated with lease			$ 1,100	$ 1,500	$ 1,100
Additional Amount | Certificates of deposit
Lessee, Lease, Description [Line Items]
Cash balance held to secure letter of credit associated with lease	$ 900