Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Detriment from a valuation allowance recorded against deferred tax asset, percentage	$ 0.19
Detriment from the recording of a valuation allowance, percentage	(19.00%)	348.00%
Oil and gas percentage depletion carryforwards	$ 9,200,000
AMT credits	5,900,000	$ 3,620,000
Valuation allowance	73,405,000	97,068,000
Decrease in valuation allowance	23,663,000
Unrecognized tax benefit	2,499,000	0	$ 0
Recognized interest accrued related to unrecognized tax benefits	0	0	$ 0
Accrued interest	0	$ 0
Credo
Operating Loss Carryforwards [Line Items]
Oil and gas percentage depletion carryforwards	9,200,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carry forwards	$ 7,500,000
Expiration date of operating loss carry forwards	Dec. 31, 2031
Domestic Tax Authority | Credo
Operating Loss Carryforwards [Line Items]
Operating loss carry forwards	$ 7,500,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carry forwards	64,200,000
State and Local Jurisdiction | Credo
Operating Loss Carryforwards [Line Items]
Operating loss carry forwards	$ 2,400,000
Minimum | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Expiration date of operating loss carry forwards	Dec. 31, 2017
Maximum | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Expiration date of operating loss carry forwards	Dec. 31, 2036