Financial Instruments Commodity Contract Volume (Details)	Dec. 31, 2013 MMcf
Natural Gas Distribution Segment [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	15,796
Natural Gas Distribution Segment [Member] | Nondesignated [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	15,796
Natural Gas Distribution Segment [Member] | Fair Value Hedging [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	0
Natural Gas Distribution Segment [Member] | Cash Flow Hedging [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	0
Nonregulated Segment [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	72,010
Nonregulated Segment [Member] | Nondesignated [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	59,095
Nonregulated Segment [Member] | Fair Value Hedging [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	(18,585)
Nonregulated Segment [Member] | Cash Flow Hedging [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	31,500