Summary of Significant Accounting Policies - Operating expense (Details) - ASU 2016-02 $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	$ 2,592
Under Topic 840
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	2,460
Effect of Change
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	132
Research and development
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	2,070
Research and development | Under Topic 840
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	1,962
Research and development | Effect of Change
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	108
General and administrative
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	522
General and administrative | Under Topic 840
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	498
General and administrative | Effect of Change
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	$ 24