Summary of Significant Accounting Policies - Additional Information 2 (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) Customer Counterparty	Dec. 31, 2017 USD ($) Customer	Dec. 31, 2016 Customer
Accounting Policies [Abstract]
Allowance for doubtful accounts on accounts receivable | $	$ 6,118	$ 7,111
Number of customers accounted more than 10% of total oil and gas revenues | Customer	1	1	1
Net derivative asset | $	$ 9,700
Number of counterparties | Counterparty	4
Number of financial institutions included in counter parties | Counterparty	20