Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment estimated to be recognized		$ 48,745	$ 38,320
Estimated reduction to accumulated deficit		$ (64,031)	$ (88,677)
Subsequent Event | Scenario, Forecast | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Leased right-of-use assets estimated to be recognized	$ 28,400
Property and equipment estimated to be recognized	1,100
Lease liability estimated to be recognized	29,400
Estimated reduction to accumulated deficit	$ 100