Financial Instruments (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Assets [Abstract]
NYMEX Fixed Price Derivative contracts	$ 0	$ 54,000
Liabilities [Abstract]
NYMEX Fixed Price Derivative contracts	13,224,000	9,012,000
Derivative Assets (Liabilities) - net [Roll Forward]
Fair value at December 31, 2016	(234)
Changes in market value	145
Settlements during the period	73
Fair Value at December 31, 2017	(16)
Recurring Basis [Member]
Assets [Abstract]
Total Assets	0	54,000
Liabilities [Abstract]
Total Liabilities	13,224,000	9,012,000
Recurring Basis [Member] | Fixed Price Derivative Contracts [Member]
Assets [Abstract]
NYMEX Fixed Price Derivative contracts	0	35,000
Liabilities [Abstract]
NYMEX Fixed Price Derivative contracts	13,208,000	8,759,000
Recurring Basis [Member] | Collars [Member]
Assets [Abstract]
NYMEX Fixed Price Derivative contracts	0	19,000
Liabilities [Abstract]
NYMEX Fixed Price Derivative contracts	16,000	253,000
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets [Abstract]
Total Assets	0	0
Liabilities [Abstract]
Total Liabilities	0	0
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed Price Derivative Contracts [Member]
Assets [Abstract]
NYMEX Fixed Price Derivative contracts	0	0
Liabilities [Abstract]
NYMEX Fixed Price Derivative contracts	0	0
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Collars [Member]
Assets [Abstract]
NYMEX Fixed Price Derivative contracts	0	0
Liabilities [Abstract]
NYMEX Fixed Price Derivative contracts	0	0
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Total Assets	0	35,000
Liabilities [Abstract]
Total Liabilities	13,208,000	8,759,000
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fixed Price Derivative Contracts [Member]
Assets [Abstract]
NYMEX Fixed Price Derivative contracts	0	35,000
Liabilities [Abstract]
NYMEX Fixed Price Derivative contracts	13,208,000	8,759,000
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Collars [Member]
Assets [Abstract]
NYMEX Fixed Price Derivative contracts	0	0
Liabilities [Abstract]
NYMEX Fixed Price Derivative contracts	0	0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets [Abstract]
Total Assets	0	19,000
Liabilities [Abstract]
Total Liabilities	16,000	253,000
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Price Derivative Contracts [Member]
Assets [Abstract]
NYMEX Fixed Price Derivative contracts	0	0
Liabilities [Abstract]
NYMEX Fixed Price Derivative contracts	0	0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Collars [Member]
Assets [Abstract]
NYMEX Fixed Price Derivative contracts	0	19,000
Liabilities [Abstract]
NYMEX Fixed Price Derivative contracts	$ 16,000	$ 253,000