Derivative Instruments and Hedging Activities (Schedule of Derivative Instruments Outstanding) (Details)	Dec. 31, 2012
January 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	13,292
Volume	412,050
Average Swap Price	105.33
January 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	13,000
Volume	403,000
Average Swap Price	3.41
February 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	13,264
Volume	371,400
Average Swap Price	105.18
February 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	13,000
Volume	364,000
Average Swap Price	3.43
March 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	12,792
Volume	396,550
Average Swap Price	104.88
March 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	11,000
Volume	341,000
Average Swap Price	3.42
April 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	12,783
Volume	383,500
Average Swap Price	104.73
April 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	11,000
Volume	330,000
Average Swap Price	3.42
May 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	12,727
Volume	394,550
Average Swap Price	104.63
May 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	10,000
Volume	310,000
Average Swap Price	3.46
June 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	12,217
Volume	366,500
Average Swap Price	104.41
June 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	9,000
Volume	270,000
Average Swap Price	3.50
July 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	9,510
Volume	294,800
Average Swap Price	104.25
July 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	9,000
Volume	279,000
Average Swap Price	3.53
August 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	6,219
Volume	192,800
Average Swap Price	104.70
August 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	8,500
Volume	263,500
Average Swap Price	3.55
September 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	6,233
Volume	187,000
Average Swap Price	104.44
September 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	8,500
Volume	255,000
Average Swap Price	3.55
October 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	5,719
Volume	177,300
Average Swap Price	103.94
October 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	8,000
Volume	248,000
Average Swap Price	3.58
November 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	6,233
Volume	187,000
Average Swap Price	103.93
November 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	7,500
Volume	225,000
Average Swap Price	3.67
December 2013 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	9,156
Volume	283,850
Average Swap Price	103.24
December 2013 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	6,500
Volume	201,500
Average Swap Price	3.83
2013 Totals [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	9,993
Volume	3,647,300
Average Swap Price	104.57
2013 Totals [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	9,562
Volume	3,490,000
Average Swap Price	3.51
January 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	10,500
Volume	325,500
Average Swap Price	100.99
February 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	10,500
Volume	294,000
Average Swap Price	100.99
March 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	10,500
Volume	325,500
Average Swap Price	100.99
April 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	8,500
Volume	255,000
Average Swap Price	101.08
May 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	8,500
Volume	263,500
Average Swap Price	101.08
June 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	8,500
Volume	255,000
Average Swap Price	101.08
July 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	8,500
Volume	263,500
Average Swap Price	101.08
August 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	5,500
Volume	170,500
Average Swap Price	100.94
September 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	5,500
Volume	165,000
Average Swap Price	100.94
October 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	5,500
Volume	170,500
Average Swap Price	100.94
November 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	5,500
Volume	165,000
Average Swap Price	100.94
December 2014 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	5,500
Volume	170,500
Average Swap Price	100.94
2014 Totals [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	7,736
Volume	2,823,500
Average Swap Price	101.06
January 2013 To December 2013 [Member] | Oil Contract [Member] | Collars [Member]
Derivative [Line Items]
Daily Average Volume	1,000
Volume	365,000
January 2013 To December 2013 [Member] | Oil Contract [Member] | Collars [Member] | Minimum [Member]
Derivative [Line Items]
Average Swap Price	80.00
January 2013 To December 2013 [Member] | Oil Contract [Member] | Collars [Member] | Maximum [Member]
Derivative [Line Items]
Average Swap Price	104.10
January 2014 To December 2014 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	5,000
Volume	1,825,000
Average Swap Price	4.01
January 2015 To December 2015 [Member] | Oil Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	1,000
Volume	365,000
Average Swap Price	97.55
January 2015 To December 2015 [Member] | Gas Contract [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Daily Average Volume	4,300
Volume	1,569,500
Average Swap Price	4.31