Leases - Supplemental balance sheet information (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases
Operating lease assets	$ 220,089	$ 380,968
Other current liabilities	$ 139,492	$ 186,967
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Accrued Liabilities, Current	Other Accrued Liabilities, Current
Operating lease liabilities	$ 83,725	$ 192,624
Total operating lease liabilities	$ 223,217	$ 379,591
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	$ 4,831,194	$ 5,141,928
Accumulated depreciation	(3,598,014)	(3,577,224)
Property and equipment, net	1,233,180	1,564,704
Other current liabilities	$ 39,957	$ 49,820
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	$ 69,207	$ 110,789
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	$ 109,164	$ 160,609
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	2 years 10 months 24 days
Weighted Average Remaining Lease Term: Finance leases	2 years 7 months 6 days	3 years 3 months 18 days
Weighted Average Discount Rate: Operating leases	8.20%	8.70%
Weighted Average Discount Rate: Finance leases	9.90%	9.60%
Property and equipment [Member]
Leases
Property and equipment, gross	$ 399,126	$ 398,875
Accumulated depreciation	(300,569)	(251,073)
Property and equipment, net	$ 98,557	$ 147,802