XML 75 R58.htm IDEA: XBRL DOCUMENT v3.10.0.1
Income taxes - Schedule of Reconciliation of Federal Statutory Rate to Company's Effective Tax Rate (Details)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Income Tax Disclosure [Abstract]      
Federal statutory rate 21.00% 35.00% 35.00%
Federal tax deferred rate change 0.00% (53.80%) 0.00%
State tax, net of federal benefit 2.60% 0.60% 0.70%
State tax deferred rate change, net of federal benefit 0.90% 0.90% 18.70%
Nondeductible business expenses 1.40% 0.00% 2.00%
Provision-to-return adjustment (3.90%) 0.00% 0.00%
Uncertain tax positions (1.30%) (1.70%) 2.00%
Stock based compensation (8.60%) (28.10%) (16.80%)
Others 1.40% (1.90%) 4.30%
Effective tax rate 13.50% (49.00%) 45.90%