Summary of Significant Accounting Policies - Operating expense (Details) - General and administrative - ASU 2016-02 $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	$ 1,944
Under Topic 840
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	1,779
Effect of Change
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense	$ 165