Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Recent Accounting Pronouncements
Practical expedients - package	true
Practical expedients - hindsight	false
Deferred rent liability			$ 799
Operating lease right-of-use asset	$ 6,295	$ 7,500
Lease liability	$ 7,502
ASU 2016-02
Recent Accounting Pronouncements
Operating lease right-of-use asset		7,499
Adjustment | ASU 2016-02
Recent Accounting Pronouncements
Deferred rent liability		(799)
Operating lease right-of-use asset		7,499
Lease liability		$ 8,300