Oil and Natural Gas Properties (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Oil And Natural Gas Properties [Line Items]
Impairment of proved and unproved oil and gas properties	$ 833	$ 92	$ 833	$ 66,740
Proved Oil and Natural Gas Properties
Oil And Natural Gas Properties [Line Items]
Depletion expenses	12,700	10,200	$ 33,000	27,900
Impairment of proved and unproved oil and gas properties				63,000
Unproved Oil and Gas Properties
Oil And Natural Gas Properties [Line Items]
Impairment of proved and unproved oil and gas properties	$ 800	$ 100		$ 3,700
Unproved Oil and Gas Properties | Minimum
Oil And Natural Gas Properties [Line Items]
Unproved oil and gas lease term			3 years
Unproved Oil and Gas Properties | Maximum
Oil And Natural Gas Properties [Line Items]
Unproved oil and gas lease term			5 years