Significant Accounting Policies - Change in Accounting Principle (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in Accounting Principle
Accumulated deficit balance	$ (168,583)	$ (45,058)
Additional paid-in capital	763,303	767,137
Total stockholders' equity	594,595	714,615	$ 738,932	$ 780,230
Deferred tax assets before valuation allowance	106,965	81,523
Valuation allowance	(106,793)	$ (56,273)
ASU 2016-09 | Early Adoption of New Accounting Principle
Change in Accounting Principle
Accumulated deficit balance	(1,300)
Additional paid-in capital	1,300
Total stockholders' equity	0
Deferred tax assets before valuation allowance	2,400
Valuation allowance	$ 2,400