Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accrued Liabilities
Accrued capital expenditures	$ 143,170	$ 155,300
Accrued gathering, compression, processing, and transportation expenses	112,937	88,850
Accrued marketing expenses	46,537	59,049
Accrued interest expense	64,641	40,861
Other accrued liabilities	89,931	99,165
Total accrued liabilities	$ 457,216	$ 443,225