Leases - Supplemental balance sheet information (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Leases
Operating lease assets	$ 471,987	$ 553,576
Other current liabilities	204,138	202,972
Operating lease liabilities	267,154	350,155
Total operating lease liabilities	471,292	553,127
Property and equipment, gross	5,171,638	5,191,840
Accumulated depreciation	(3,509,710)	(3,440,267)
Property and equipment, net	1,661,928	1,751,573
Other current liabilities	50,860	48,678
Other long-term liabilities	137,949	163,939
Total finance lease liabilities	$ 188,809	$ 212,617
Weighted Average Remaining Lease Term: Operating leases	3 years 1 month 6 days	3 years 4 months 24 days
Weighted Average Remaining Lease Term: Finance leases	3 years 9 months 18 days	4 years 2 months 12 days
Weighted Average Discount Rate: Operating leases	9.00%	9.10%
Weighted Average Discount Rate: Finance leases	9.50%	9.50%
Property and equipment [Member]
Leases
Property and equipment, gross	$ 398,875	$ 399,764
Accumulated depreciation	(226,325)	(201,873)
Property and equipment, net	$ 172,550	$ 197,891