Impairment of Natural Gas and Crude Oil Properties (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Impairment of natural gas and crude oil properties [Line Items]
Impairment of proved properties	$ 1,084	$ 1,631	$ 2,053	$ 1,919
Amortization of Individually Insignificant Unproved Properties	54	2,773	86	5,257
Impairment of Oil and Gas Properties	1,138	4,404	2,139	7,176
Land and buildings	3,032	0	3,032	0
Impairment of properties and equipment	$ 4,170	$ 4,404	$ 5,171	$ 7,176