Financial Instruments Commodity Contract Volume (Details)	Mar. 31, 2014 MMcf
Natural Gas Distribution Segment [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	8,428
Natural Gas Distribution Segment [Member] | Nondesignated [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	8,428
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	62,000
Nonregulated Segment [Member] | Nondesignated [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	45,975
Nonregulated Segment [Member] | Fair Value Hedging [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	(5,770)
Nonregulated Segment [Member] | Cash Flow Hedging [Member]
Commodity Contract Outstanding Volumes [Line Items]
Investment Contract Volume	21,795