Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Crude oil and natural gas sales	$ 1,273,238	$ 704,818	$ 3,524,618	$ 1,965,216
Gain (loss) on natural gas derivatives, net	(2,025)	8,602	(4,536)	83,482
Crude oil and natural gas service operations	10,938	13,323	40,210	24,959
Total revenues	1,282,151	726,743	3,560,292	2,073,657
Transportation expenses	46,008	0	142,559	0
Net income	314,169	$ 10,621	790,580	$ (52,467)
Previous Revenue Recognition
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Crude oil and natural gas sales	1,227,230		3,382,059
Gain (loss) on natural gas derivatives, net	(2,025)		(4,536)
Crude oil and natural gas service operations	10,938		40,210
Total revenues	1,236,143		3,417,733
Transportation expenses	0		0
Net income	314,169		790,580
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	46,008		142,559
Gain (loss) on natural gas derivatives, net	0		0
Crude oil and natural gas service operations	0		0
Total revenues	46,008		142,559
Transportation expenses	46,008		142,559
Net income	$ 0		$ 0