Fair Value Measurements - Hierarchy of Fair Value, Assets and Liabilities Measured on Recurring Basis (Detail) - Recurring - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets:
Total assets	$ 1,320	$ 107,018
Total liabilities	19,815	104
Money market funds
Assets:
Total assets	146	143
Commodity derivative instruments
Assets:
Total assets	1,174	106,875
Total liabilities	19,815	104
Level 1
Assets:
Total assets	146	143
Total liabilities	0	0
Level 1 | Money market funds
Assets:
Total assets	146	143
Level 1 | Commodity derivative instruments
Assets:
Total assets	0	0
Total liabilities	0	0
Level 2
Assets:
Total assets	1,174	106,875
Total liabilities	19,815	104
Level 2 | Money market funds
Assets:
Total assets	0	0
Level 2 | Commodity derivative instruments
Assets:
Total assets	1,174	106,875
Total liabilities	19,815	104
Level 3
Assets:
Total assets	0	0
Total liabilities	0	0
Level 3 | Money market funds
Assets:
Total assets	0	0
Level 3 | Commodity derivative instruments
Assets:
Total assets	0	0
Total liabilities	$ 0	$ 0