Summary of Significant Accounting Policies - Additional Information 2 (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Customer Counterparty	Dec. 31, 2016 USD ($) Customer	Dec. 31, 2015 Customer
Summary Of Significant Accounting Policies [Line Items]
Allowance for doubtful accounts on accounts receivable	$ 7,111	$ 5,559
Number of customers accounted more than 10% of total oil and gas revenues | Customer	1	1	1
Net derivative asset	$ 28,200
Number of counterparties | Counterparty	5
Number of financial institutions included in counter parties | Counterparty	19
Accounting Standards Update 2016-09
Summary Of Significant Accounting Policies [Line Items]
Recognition of an excess tax deficiency in provision for income taxes rather than paid-in capital		$ 2,100
Cumulative-effect adjustments to retained earnings (deficit) and reduced deferred tax liability		$ 101,100