Derivative Financial Instruments (Derivative Instruments, Gain (Loss) (Details) (Swap [Member])	12 Months Ended
	Dec. 31, 2014 MMBTuPerDay
Product [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Jan. 01, 2015
Derivative, Maturity Date	Mar. 31, 2015
Underlying, Derivative Volume	500
Derivative, Swap Type, Fixed Price	3.980
Product One [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Jan. 01, 2015
Derivative, Maturity Date	Mar. 31, 2015
Underlying, Derivative Volume	500
Derivative, Swap Type, Fixed Price	4.075
Product Two [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Jan. 01, 2015
Derivative, Maturity Date	Mar. 31, 2015
Underlying, Derivative Volume	501
Derivative, Swap Type, Fixed Price	3.560
Product Three [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Jan. 01, 2015
Derivative, Maturity Date	Mar. 31, 2015
Underlying, Derivative Volume	3,600
Derivative, Swap Type, Fixed Price	13.000
Product Four [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Apr. 01, 2015
Derivative, Maturity Date	Apr. 30, 2015
Underlying, Derivative Volume	2,500
Derivative, Swap Type, Fixed Price	13.000
Product Five [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	May 01, 2015
Derivative, Maturity Date	May 31, 2015
Underlying, Derivative Volume	1,390
Derivative, Swap Type, Fixed Price	13.000
Product Six [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Jun. 01, 2015
Derivative, Maturity Date	Jun. 30, 2015
Underlying, Derivative Volume	950
Derivative, Swap Type, Fixed Price	13.000
Product Seven [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Jul. 01, 2015
Derivative, Maturity Date	Jul. 31, 2015
Underlying, Derivative Volume	890
Derivative, Swap Type, Fixed Price	13.000