Summary of Significant Accounting Policies - Recently Adopted Accounting Policies - ASU 2016-09 (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jan. 01, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in accumulated deficit	$ (44,682)		$ (293,896)
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for uncertain tax position		$ 1,946
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in accumulated deficit	$ (10,271)		$ (293,896)
Accumulated Deficit | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income tax assets, net		293,896
Decrease in accumulated deficit		$ 293,896