Leases - Components of lease expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Leases
Operating lease cost	$ 61,750	$ 72,739	$ 185,273	$ 234,787
Short-term lease cost	3,148	3,010	9,548	34,436
Amortization of right-of-use assets	12,374	6,773	37,122	16,686
Interest on lease liabilities	4,270	2,495	13,602	4,775
Total finance lease cost	16,644	9,268	50,724	21,461
Total lease costs	$ 81,542	$ 85,017	$ 245,545	$ 290,684