Derivative Instruments and Hedging Activities (Derivatives Fair Value By Balance Sheet Location) (Details) (Not Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Derivative Asset, Fair Value, Net	$ 2,075	$ 1,924
Derivative Liability, Fair Value, Net	(144)	(241)
Derivative, Fair Value, Net	1,931	1,683
Natural gas [Member] | Current Liabilities - Fair Market Value of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Liability, Fair Value, Gross Liability	(106)	(125)
Derivative Assets (Liability), Fair Value, Gross Liability Net	106	125
Natural gas [Member] | Non-current liabilities - Other long-term liabilities [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Liability, Fair Value, Gross Liability	(38)	(116)
Derivative Assets (Liability), Fair Value, Gross Liability Net	38	116
Crude oil [Member] | Current assets - Fair market value of derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,647	1,674
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Assets (Liability), Fair Value, Gross Asset Net	1,647	1,674
Crude oil [Member] | Noncurrent Assets - Other Long-Term Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	428	250
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Assets (Liability), Fair Value, Gross Asset Net	$ 428	$ 250