Summary of Significant Accounting Policies - Adoption of New Accounting Pronouncements (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right of use asset - operating lease	$ 4,412	$ 4,452
Lease liability, current - operating lease	175	111
Deferred rent, current			$ 150
Lease liability, operating lease	$ 5,108	5,156
Deferred rent			$ 665
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right of use asset - operating lease		4,452
Lease liability, current - operating lease		111
Deferred rent, current		(150)
Lease liability, operating lease		5,156
Deferred rent		$ (665)