Fair Value Measurements - Hierarchy of Fair Value, Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets:
Total assets	$ 503	$ 156,215
Total liabilities	72,183
Money market funds
Assets:
Total assets	141	742
Commodity derivative instruments
Assets:
Total assets	362	155,473
Total liabilities	72,183
Level 1
Assets:
Total assets	141	742
Total liabilities	0
Level 1 | Money market funds
Assets:
Total assets	141	742
Level 1 | Commodity derivative instruments
Assets:
Total assets	0	0
Total liabilities	0
Level 2
Assets:
Total assets	362	155,473
Total liabilities	72,183
Level 2 | Money market funds
Assets:
Total assets	0	0
Level 2 | Commodity derivative instruments
Assets:
Total assets	362	155,473
Total liabilities	72,183
Level 3
Assets:
Total assets	0	0
Total liabilities	0
Level 3 | Money market funds
Assets:
Total assets	0	0
Level 3 | Commodity derivative instruments
Assets:
Total assets	0	$ 0
Total liabilities	$ 0