Leases - Components of lease expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases
Operating lease cost	$ 246,523	$ 297,181
Short-term lease cost	11,409	37,686
Amortization of right-of-use assets	49,496	29,134
Interest on lease liabilities	17,595	9,826
Total finance lease cost	67,091	38,960
Total lease costs	$ 325,023	$ 373,827