Income taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income tax expense, tax cuts and jobs act	$ 14,485
Unrecognized tax benefits		$ 140,327
Unrecognized tax benefits that would impact effective tax rate if recognized		140,327
Accrued interest related to the gross unrecognized tax benefits excluded from the unrecognized tax benefits		23,342
Decrease in unrecognized tax benefits that is reasonably possible (up to)		$ 100,000