Leases - Maturities of lease liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Maturities of lease liabilities: Operating lease
2020 (remaining nine months)	$ 181,706
2021	203,198
2022	130,570
2023	26,599
2024	11,112
Thereafter	42,350
Total lease payments	595,535
Less: Imputed interest	(79,757)
Total operating lease liabilities	515,778	$ 553,127
Less: Current portion	(205,068)	(202,972)
Operating lease liabilities	310,710	350,155
Maturities of lease liabilities: Finance lease
2020 (remaining nine months)	50,056
2021	66,279
2022	50,227
2023	42,862
2024	32,147
Total lease payments	241,571
Less: Imputed interest	(40,407)
Total finance lease liabilities	201,164	212,617
Less: Current portion	(49,743)	(48,678)
Long-term portion of lease obligations	151,421	$ 163,939
Future minimum payments for total lease liabilities
2020 (remaining nine months)	231,762
2021	269,477
2022	180,797
2023	69,461
2024	43,259
Thereafter	42,350
Total lease payments	837,106
Less: Imputed interest	(120,164)
Total	716,942
Less: Current portion	(254,811)
Long-term portion of lease obligations	$ 462,131