Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued Liabilities
Accrued capital expenditures	$ 113,237	$ 155,300
Accrued gathering, compression, processing, and transportation expenses	148,032	88,850
Accrued marketing expenses	67,082	59,049
Accrued interest expense	43,444	40,861
Other accrued liabilities	93,275	99,165
Total accrued liabilities	$ 465,070	$ 443,225