Commitments and Contingencies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Long-term Purchase Commitment [Line Items]
Total future drilling commitments at balance sheet date	$ 107
Drilling commitments due year one	106
Drilling commitments due year two	1
Estimated lease assets and liabilities drilling rig	$ 13
Future Drilling Commitments End Date	2020-02
Pipeline Transportation and Processing Commitments [Member]
Long-term Purchase Commitment [Line Items]
Future commitment, end date	2028
Future commitment, total	$ 1,832
Future commitment, due year one	241
Future commitment, due year two	273
Future commitment, due year three	254
Future commitment, due year four	249
Future commitment, due year five	248
Future commitments, thereafter	$ 566