Clayton Williams Energy Acquisition (Details) $ / shares in Units, a in Thousands, shares in Millions, $ in Millions		3 Months Ended
	Apr. 24, 2017 USD ($) a $ / shares shares	Mar. 31, 2017 USD ($) well
Business Acquisition [Line Items]
Number of Wells Operated by Company | well		4
Consideration		$ 300
Subsequent Event [Member]
Business Acquisition [Line Items]
Stock price ($ per share) | $ / shares	$ 34.17
Subsequent Event [Member] | Clayton Williams Energy
Business Acquisition [Line Items]
Area acquired (acres) | a	118
Shares exchange in acquisition (shares) | shares	55
Consideration	$ 1,900
Cash consideration	665
Consideration	2,600
Credit facility draw	$ 1,300