Risk Management Activities (The Effect Of Derivative Instruments Reclassified To Statements Of Consolidated Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Cash Flow Hedging [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ 0.1		$ 0.1
Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net, Total	(0.5)		(0.3)
Fair Value Hedging [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	(10.4)		(9.7)
Amount of Gain (Loss) Recognized in Income on Related Hedged Items	10.4		9.7
Not Designated as Hedging Instrument [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	6.9	[1]	(6.4)	[1]
Interest Expense [Member] | Cash Flow Hedging [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net, Total	(0.4)		(0.4)
Cost Of Sales [Member] | Cash Flow Hedging [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net, Total	(0.1)		0.1
Commodity Price Risk Programs [Member] | Cash Flow Hedging [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	0.1		0.1
Commodity Price Risk Programs [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Regulatory Deferred	6.9		(6.6)
Commodity Price Risk Programs [Member] | Gas Distribution Revenues [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	0	[1]	0.1	[1]
Commodity Price Risk Programs [Member] | Cost Of Sales [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	6.9	[1]	(6.7)	[1]
Commodity Price Risk Programs [Member] | (Loss) Income From Discontinued Operations [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	0	[1]	0.2	[1]
Interest Rate Risk Activities [Member] | Cash Flow Hedging [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	0		0
Interest Rate Risk Activities [Member] | Interest Expense [Member] | Fair Value Hedging [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	(10.4)		(9.7)
Fixed Rate Debt Hedges [Member] | Interest Expense [Member] | Fair Value Hedging [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in Income on Related Hedged Items	$ 10.4		$ 9.7

[1] For the amounts of realized/unrealized gain (loss) recognized in income on derivatives disclosed in the table above, gains of $6.9 million and $6.6 million for the three months ended March 31, 2014 and 2013, respectively, were deferred as allowed per regulatory orders. These amounts will be amortized to income over future periods of up to twelve months as specified in a regulatory order.