Income Taxes - Schedule of Overall Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax benefit based on the federal statutory rate	34.00%	34.00%	34.00%
State income taxes, net of federal benefit (as a percent)	9.40%	3.20%	2.40%
Nondeductible expenses (as a percent)	(1.20%)	(1.70%)	(0.30%)
Change in valuation allowance (as a percent)	(130.00%)	(33.00%)	(30.70%)
Stock-based compensation (as a percent)	86.50%	(4.10%)	(6.40%)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	7.50%	0.00%	0.00%
Other (as a percent)	0.00%	0.00%	0.10%
Overall effective income tax rate	6.20%	(1.60%)	(0.90%)