Derivative Commodity Instruments Derivative Commodity - Reclassification (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivatives, Fair Value [Line Items]
Reclassification from comprehensive income, net of tax			$ 3,600,000
Revenue, Net	(497,761,000)	(272,038,000)	(1,065,136,000)	(875,350,000)
Production Period, Year One | NYMEX Swaps | Crude Oil
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	2,502,000		2,502,000
Average contract price			92.66
Production Period, Year One | NYMEX Swaps | Natural Gas
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	2,600,000.0		2,600,000.0
Average contract price ($ per Mcf)			4.57
Production Period, Year One | WTS/WTI Basis Swaps | Crude Oil
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	300,000		300,000
Average contract price			(3.30)
Production Period, Year One | WTI/WTI Basis Swaps | Crude Oil
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	600,000		600,000
Average contract price			(3.08)
Production Period, Year One | Liquids Swaps | Natural Gas Liquids
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	18,500,000.0		18,500,000.0
Average contract price			0.93
Production Period, Year One | Basin Specific Swaps, San Juan | Natural Gas
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	7,580,000.00		7,580,000.00
Average contract price ($ per Mcf)			4.62
Production Period, Year One | Basin Specific Swaps - Permain | Natural Gas
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	2,600,000.0		2,600,000.0
Average contract price ($ per Mcf)			3.81
Production Period, Year One | San Juan Basis Swaps | Natural Gas
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	1.48		1.48
Average contract price ($ per Mcf)			(0.09)
Production Period, Year One | Permian Basis Swaps | Natural Gas
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	0.6		0.6
Average contract price ($ per Mcf)			(0.17)
Production Period, Year Two | NYMEX Swaps | Crude Oil
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	8,280,000		8,280,000
Average contract price			89.30
Production Period, Year Two | WTS/WTI Basis Swaps | Crude Oil
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	2,160,000		2,160,000
Average contract price			(4.30)
Production Period, Year Two | WTI/WTI Basis Swaps | Crude Oil
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	6,120,000		6,120,000
Average contract price			(5.11)
Production Period, Year Two | Basin Specific Swaps, San Juan | Natural Gas
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	23,000,000		23,000,000
Average contract price ($ per Mcf)			4.13
Production Period, Year Two | Basin Specific Swaps - Permain | Natural Gas
Derivatives, Fair Value [Line Items]
Total Hedged Volumes	6,000,000		6,000,000
Average contract price ($ per Mcf)			4.20
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Gain from Discontinued Hedge Accounting
Derivatives, Fair Value [Line Items]
Revenue, Net			$ 1,700,000