Derivative Instruments and Hedging Activities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 MMBTU
Derivative Line [Items]
Derivative financial instruments, fair value, net	$ 9.6
Cash flow commodity hedge deferred net gain to be reclassified within twelve months	11.0
Cash flow interest rate swaps deferred net loss to be reclassified within twelve months	$ 1.1
Instruments - Swaps [Member] | Year 2014 [Member] | Natural Gas [Member]
Derivative Line [Items]
Notional volumes of commodity hedges (per day)	54,050
Instruments - Swaps [Member] | Year 2014 [Member] | NGL [Member]
Derivative Line [Items]
Notional volumes of commodity hedges (per day)	1,125
Instruments - Swaps [Member] | Year 2014 [Member] | Condensate [Member]
Derivative Line [Items]
Notional volumes of commodity hedges (per day)	2,450
Instruments - Swaps [Member] | Year 2015 [Member] | Natural Gas [Member]
Derivative Line [Items]
Notional volumes of commodity hedges (per day)	40,551
Instruments - Swaps [Member] | Year 2015 [Member] | NGL [Member]
Derivative Line [Items]
Notional volumes of commodity hedges (per day)	0
Instruments - Swaps [Member] | Year 2015 [Member] | Condensate [Member]
Derivative Line [Items]
Notional volumes of commodity hedges (per day)	0
Instruments - Swaps [Member] | Year 2016 [Member] | Natural Gas [Member]
Derivative Line [Items]
Notional volumes of commodity hedges (per day)	25,500
Instruments - Swaps [Member] | Year 2016 [Member] | NGL [Member]
Derivative Line [Items]
Notional volumes of commodity hedges (per day)	0
Instruments - Swaps [Member] | Year 2016 [Member] | Condensate [Member]
Derivative Line [Items]
Notional volumes of commodity hedges (per day)	0