Investment in Unconsolidated Affiliates Related Party Transactions (Details) (Og and E [Member], USD $) In Millions, unless otherwise specified	2 Months Ended	3 Months Ended	6 Months Ended	2 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Operating Costs Charged [Member]	Jun. 30, 2013 Operating Costs Charged [Member]	Jun. 30, 2013 Natural Gas Transportation [Member]	Jun. 30, 2013 Natural Gas Storage [Member]	Jun. 30, 2013 Natural Gas Purchases [Member]
Related Party Transaction [Line Items]
Operating expenses		$ 7.9	$ 14.6
Related Party Transaction, Due from (to) Related Party						1.2
Revenue from Related Parties	1.3
Related Party Transaction, Purchases from Related Party				$ 5.8	$ 2.3	$ 2.5	[1]

[1] At June 30, 2013, there was $1.2 million of natural gas purchases recorded for these activities.