Risk Management And Hedging Activities (Schedule Of Derivatives Accounted For As Cash Flow Hedges) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012	Sep. 30, 2011
Derivative [Line Items]
Derivative loss reclassified					$ 0.6
Interest Rate Derivatives [Member]
Derivative [Line Items]
Gain (Loss) Recognized in AOCI on Derivatives - Effective Portion	(0.4)		(5.3)		(0.6)	(9.5)
Loss Reclassified From AOCI to Earnings-Effective Portion	(0.6)		(5.1)	[1]	(9.9)	(15.4)	[1]
Loss Recognized in Income on Derivatives-Ineffective Portion and Amount Excluded From Effectiveness Testing			(0.1)	[1]	(2.1)	(0.2)	[1],[2]
Deferred Losses in AOCI Expected to be Reclassified into Earnings Over the Next 12 Months	(3.2)				(3.2)
Commodity Derivatives [Member]
Derivative [Line Items]
Gain (Loss) Recognized in AOCI on Derivatives - Effective Portion	0.6		(0.2)			(0.3)
Loss Reclassified From AOCI to Earnings-Effective Portion			(0.1)			(0.2)	[3]
Loss Recognized in Income on Derivatives-Ineffective Portion and Amount Excluded From Effectiveness Testing				[4]	(0.1)		[5]
Deferred Losses in AOCI Expected to be Reclassified into Earnings Over the Next 12 Months
Foreign Currency Derivatives [Member]
Derivative [Line Items]
Gain (Loss) Recognized in AOCI on Derivatives - Effective Portion	0.5	[4]
Loss Reclassified From AOCI to Earnings-Effective Portion		[4]		[4]
Loss Recognized in Income on Derivatives-Ineffective Portion and Amount Excluded From Effectiveness Testing		[4]		[4]
Deferred Losses in AOCI Expected to be Reclassified into Earnings Over the Next 12 Months		[4]

[1] Included in interest expense in our condensed consolidated statements of operations.

[2] For the nine months ended September 30, 2012, $0.6 million of derivative losses were reclassified from AOCI to current period earnings as a result of the discontinuance of cash flow hedges related to certain forecasted transactions that are not probable of occurring.

[3] Included in gains (losses) from commodity derivative activity, net in our condensed consolidated statements of operations.

[4] Relates to Discovery, our unconsolidated affiliate.

[5] For the nine months ended September 30, 2012 and 2011, no derivative gains or losses were reclassified from AOCI to current period earnings as a result of the discontinuance of cash flow hedges related to certain forecasted transactions that are not probable of occurring. The ineffective portion is included in gains (losses) from commodity derivative activity, net in our condensed consolidated statements of operations.