Income taxes - Narrative (Details) $ in Thousands |
Sep. 30, 2017
USD ($)
|
---|---|
Income Tax Disclosure [Abstract] | |
Unrecognized tax benefits | $ 150,651 |
Amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate | 97,900 |
Accrued interest related to the gross unrecognized tax benefits excluded from the unrecognized tax benefits | 16,724 |
Significant decrease in unrecognized tax benefits that is reasonably possible | $ 110,000 |