Annual report pursuant to Section 13 and 15(d)

Income Taxes - Reconciliation of the Federal Statutory Income Tax Rate to the Effective Income Tax Rate (Details)

v3.8.0.1
Income Taxes - Reconciliation of the Federal Statutory Income Tax Rate to the Effective Income Tax Rate (Details)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]      
U.S. Statutory rate 34.00% 34.00% 34.00%
State income taxes, net of federal benefit 0.37% 0.88% 2.00%
Stock-based compensation (30.40%) (23.74%) 0.65%
Change in valuation allowance (2.59%) (4.26%) (7.91%)
R&D credit, net of reserve (1.43%) (1.75%) (2.97%)
Expiration of net operating losses 2.76% 4.51% 1.17%
Reassessment of prior year APIC benefit     (3.11%)
Effect of U.S tax law change 25.55%    
Other 0.92% 0.07% (2.50%)
Effective income tax rate 29.18% 9.71% 21.33%