New Accounting Standards - Schedule of Impact of Adoption of New Revenue Recognition Standard (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($) $ / Mcfe	Mar. 31, 2017 USD ($)
Revenues and other income:
Natural gas, NGLs and oil sales	$ 696,629	$ 559,450
Natural gas, NGLs and oil sales (in dollars per share) \| $ / Mcfe	3.53
Costs and expenses:
Transportation, gathering, processing and compression	$ 244,628	177,648
Transportation, gathering, processing and compression (in dollars per share) \| $ / Mcfe	1.24
Net income	$ 49,238	$ 170,111
Accounting Standards Update 2014-09 \| Previous Revenue Recognition
Revenues and other income:
Natural gas, NGLs and oil sales	$ 658,802
Natural gas, NGLs and oil sales (in dollars per share) \| $ / Mcfe	3.34
Costs and expenses:
Transportation, gathering, processing and compression	$ 206,801
Transportation, gathering, processing and compression (in dollars per share) \| $ / Mcfe	1.05
Net income	$ 49,238
Accounting Standards Update 2014-09 \| Increase
Revenues and other income:
Natural gas, NGLs and oil sales	$ 37,827
Natural gas, NGLs and oil sales (in dollars per share) \| $ / Mcfe	0.19
Costs and expenses:
Transportation, gathering, processing and compression	$ 37,827
Transportation, gathering, processing and compression (in dollars per share) \| $ / Mcfe	0.19
Net income	$ 0