Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Crude oil and natural gas sales	$ 1,137,528	$ 626,548	$ 2,251,380	$ 1,260,398
Gain (loss) on natural gas derivatives, net	(12,685)	28,022	(2,511)	74,880
Crude oil and natural gas service operations	12,270	6,916	29,272	11,636
Total revenues	1,137,113	661,486	2,278,141	1,346,914
Transportation expenses	47,254	0	96,551	0
Net income	242,464	$ (63,557)	476,410	$ (63,088)
Previous Revenue Recognition
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Crude oil and natural gas sales	1,090,274		2,154,829
Gain (loss) on natural gas derivatives, net	(12,685)		(2,511)
Crude oil and natural gas service operations	12,270		29,272
Total revenues	1,089,859		2,181,590
Transportation expenses	0		0
Net income	242,464		476,410
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Crude oil and natural gas sales	47,254		96,551
Gain (loss) on natural gas derivatives, net	0		0
Crude oil and natural gas service operations	0		0
Total revenues	47,254		96,551
Transportation expenses	47,254		96,551
Net income	$ 0		$ 0