Lease costs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating lease cost	$ 43,759
Variable lease cost	1,555
Short-term lease cost	120,030
Total lease costs	$ 165,344
Weighted average remaining lease term	3 years 1 month 17 days
Weighted average discount rate	4.41%
Cash paid for amounts included in the measurement of lease liabilities	$ 43,477