Leases - Components of lease expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases
Operating lease cost	$ 60,023	$ 61,715
Short-term lease cost	4,236	2,667
Amortization of right-of-use assets	12,374	12,448
Interest on lease liabilities	3,716	4,798
Total finance lease cost	16,090	17,246
Total lease costs	$ 80,349	$ 81,628