Leases - Maturities of lease liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Maturities of lease liabilities: Operating lease
2019 (remaining six months)	$ 144,459
2020	233,895
2021	193,126
2022	123,971
2023	23,929
Thereafter	51,054
Total lease payments	770,434
Less: Imputed interest	(116,470)
Total operating lease liabilities	653,964
Other current liabilities	(217,390)
Operating lease liabilities	436,574
Maturities of lease liabilities: Finance lease
2019 (remaining six months)	11,012
2020	22,024
2021	22,026
2022	7,363
Total lease payments	62,425
Less: Imputed interest	(6,302)
Total finance lease liabilities	56,123	$ 66,984
Less: Current portion	(18,466)
Long-term portion of lease obligations	37,657
Future minimum payments for total lease liabilities
2019 (remaining six months)	155,471
2020	255,919
2021	215,152
2022	131,334
2023	23,929
Thereafter	51,054
Total lease payments	832,859
Less: Imputed interest	(122,772)
Total	710,087
Less: Current portion	(235,856)
Long-term portion of lease obligations	$ 474,231