Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Major Components of Property and Equipment

The major components of property and equipment, at cost, are as follows:

	Estimated Useful Life	December 31,
		2016			2017
	Years	(In thousands)
Oil and gas properties (1)	—	$	794,634		$	923,237
Equipment and other	3-39	15,227			15,648
Drilling rig	15	23,342			23,488
		833,203			962,373
Accumulated depreciation, depletion, amortization and impairment		(696,892		)	(724,606		)
Net Property and Equipment		$	136,311		$	237,767