XML 87 R75.htm IDEA: XBRL DOCUMENT v3.8.0.1
Income taxes - Tax Rate Reconciliation (Details)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Reconciliation of the U.S. statutory income tax rate to the entity's effective tax rate      
Federal income tax at statutory rate 34.00% 34.00% 34.00%
State income tax (benefit), net of federal benefit (1.01%) 3.05% (0.43%)
Permanent differences (8.48%) (3.70%) (6.61%)
Research and development 19.53% 16.66% 19.50%
(Increase) decrease to valuation allowance 29.10% (30.72%) (20.87%)
Change in deferred tax assets (64.12%) 0.00% 0.00%
Foreign tax rate differential (10.33%) (19.84%) (24.06%)
Benefit (expense) allocated from other comprehensive income (0.26%) 0.14% 0.00%
Other (0.15%) 0.01% (1.82%)
Effective income tax rate (1.72%) (0.40%) (0.29%)