Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accrued Liabilities
Accrued capital expenditures	$ 123,911	$ 155,300
Accrued gathering, compression, processing, and transportation expenses	94,693	88,850
Accrued marketing expenses	61,917	59,049
Accrued interest expense	63,451	40,861
Other accrued liabilities	78,645	99,165
Total accrued liabilities	$ 422,617	$ 443,225