Income Taxes - Statutory Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliations of the statutory federal income tax rate and effective tax rate
Tax at federal statutory rate	$ (25,797)	$ (19,715)	$ (5,661)
State and local tax	(1,133)	(3,189)	(916)
Non-deductible stock compensation	1,291	688	210
Non-deductible expenses	382	158	87
Benefit due to tax rate change	(89)
Change in valuation allowance	25,856	22,094	6,668
Income tax provision	$ 510	$ 36	$ 388