Leases - Supplemental balance sheet information (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Leases
Operating lease assets	$ 188,927	$ 220,089
Other current liabilities	$ 125,818	$ 139,492
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Accrued Liabilities, Current	Other Accrued Liabilities, Current
Operating lease liabilities	$ 67,450	$ 83,725
Total operating lease liabilities	$ 193,268	$ 223,217
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Operating lease liabilities, Other Accrued Liabilities, Current	Operating lease liabilities, Other Accrued Liabilities, Current
Property and equipment, gross	$ 4,771,884	$ 4,831,194
Accumulated depreciation	(3,610,023)	(3,598,014)
Property and equipment, net	1,161,861	1,233,180
Other current liabilities	$ 39,024	$ 39,957
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Long-term Debt and Capital Lease Obligations, Current	Long-term Debt and Capital Lease Obligations, Current
Other long-term liabilities	$ 59,970	$ 69,207
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-term Debt, Excluding Current Maturities	Long-term Debt, Excluding Current Maturities
Total finance lease liabilities	$ 98,994	$ 109,164
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Contract with Customer, Liability, Noncurrent and Other Long Term Liabilities	Contract with Customer, Liability, Noncurrent and Other Long Term Liabilities
Weighted Average Remaining Lease Term: Operating leases	3 years	3 years
Weighted Average Remaining Lease Term: Finance leases	2 years 6 months	2 years 7 months 6 days
Weighted Average Discount Rate: Operating leases	8.10%	8.20%
Weighted Average Discount Rate: Finance leases	10.00%	9.90%
Property and equipment [Member]
Leases
Property and equipment, gross	$ 399,126	$ 399,126
Accumulated depreciation	(313,034)	(300,569)
Property and equipment, net	$ 86,092	$ 98,557