Leases - Maturities of lease liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Maturities of lease liabilities: Operating lease
2019 (remaining three months)	$ 62,542
2020	237,282
2021	196,847
2022	125,791
2023	24,387
Thereafter	51,402
Total lease payments	698,251
Less: Imputed interest	(102,746)
Total operating lease liabilities	595,505
Other current liabilities	(200,532)
Operating lease liabilities	394,973
Maturities of lease liabilities: Finance lease
2019 (remaining three months)	16,231
2020	66,207
2021	66,247
2022	50,226
2023	42,862
Thereafter	32,145
Total lease payments	273,918
Less: Imputed interest	(50,112)
Total finance lease liabilities	223,806	$ 66,984
Less: Current portion	(47,399)
Long-term portion of lease obligations	176,407
Future minimum payments for total lease liabilities
2019 (remaining three months)	78,773
2020	303,489
2021	263,094
2022	176,017
2023	67,249
Thereafter	83,547
Total lease payments	972,169
Less: Imputed interest	(152,858)
Total	819,311
Less: Current portion	(247,931)
Long-term portion of lease obligations	$ 571,380