Fair Value Measurements - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) Counterparty	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Interest and dividends	$ 204,000	$ 181,000	$ 323,000	$ 317,000
Mark-to-market gain (loss)	1,500,000	1,200,000	3,000,000	1,400,000
Impairment on natural gas and oil properties	0	$ 0	0	43,040,000
Allowance for doubtful accounts on accounts receivable	5,861,000		$ 5,861,000		$ 5,559,000
Number of financial institutions included in counter parties | Counterparty			22
Number of counterparties | Counterparty			5
Net derivative asset	9,500,000		$ 9,500,000
Western Oklahoma
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment on natural gas and oil properties	$ 0		$ 0	$ 43,000,000