Leases - Maturities of lease liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Maturities of lease liabilities: Operating lease
2020	$ 239,660
2021	199,062
2022	127,300
2023	24,571
2024	9,191
Thereafter	42,008
Total lease payments	641,792
Less: Imputed interest	(88,665)
Total operating lease liabilities	553,127
Other current liabilities	(202,972)
Operating lease liabilities	350,155
Maturities of lease liabilities: Finance lease
2020	66,285
2021	66,279
2022	50,227
2023	42,862
2024	32,147
Total lease payments	257,800
Less: Imputed interest	(45,183)
Total finance lease liabilities	212,617	$ 66,984
Less: Current portion	(48,678)
Long-term portion of lease obligations	163,939
Future minimum payments for total lease liabilities
2020	305,945
2021	265,341
2022	177,527
2023	67,433
2024	41,338
Thereafter	42,008
Total lease payments	899,592
Less: Imputed interest	(133,848)
Total	765,744
Less: Current portion	(251,650)
Long-term portion of lease obligations	$ 514,094