Leases - Narrative (Details) $ in Thousands		3 Months Ended	12 Months Ended
	Oct. 01, 2019 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2020 USD ($) sublease_option	Sep. 30, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating leases right-of-use assets			$ 22,427
Operating lease liabilities, current			2,045
Operating lease liabilities - long-term			21,620
Accumulated deficit			32,443	$ 39,555
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Gain recognized on lease modification			121	$ 0
Operating lease liability			23,665
Increase to right-of-use assets			24,700
Increase to lease liabilities			$ 25,200
Sublease term			5 years
Number of sublease extension options | sublease_option			2
Sublease option extension period			1 year
Facilities and Equipment | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Remaining lease term			7 months 6 days
Facilities and Equipment | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Remaining lease term			10 years 6 months
Lease Modification
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating leases right-of-use assets	$ 7,300
Gain recognized on lease modification		$ 100
Operating lease liability	7,200
Cumulative-effect adjustment for adoption of ASC 842
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating leases right-of-use assets	17,398
Operating lease liabilities, current	3,645
Operating lease liabilities - long-term	14,372
Accumulated deficit	$ 2