Investment in Unconsolidated Affiliates Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended		3 Months Ended	5 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	5 Months Ended	3 Months Ended	5 Months Ended	3 Months Ended		5 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Og and E [Member]	Sep. 30, 2013 Og and E [Member]	Sep. 30, 2013 Operating Costs Charged [Member] Og and E [Member]	Sep. 30, 2013 Operating Costs Charged [Member] Og and E [Member]	Sep. 30, 2013 Natural Gas Transportation [Member] Og and E [Member]	Sep. 30, 2013 Natural Gas Transportation [Member] Og and E [Member]	Sep. 30, 2013 Natural Gas Storage [Member] Og and E [Member]	Sep. 30, 2013 Natural Gas Storage [Member] Og and E [Member]	Sep. 30, 2013 Natural Gas Purchases [Member] Og and E [Member]		Sep. 30, 2013 Natural Gas Purchases [Member] Og and E [Member]
Related Party Transaction [Line Items]
Distributions from unconsolidated affiliates	$ 17.4	$ 17.4	$ 0
Operating expenses						6.6	10.9
Related Party Transaction, Due from (to) Related Party												1.4		1.4
Electricity to power electric compression assets				3.9	5.2
Related Party Transaction, Purchases from Related Party								$ 8.7	$ 14.5	$ 3.1	$ 5.4	$ 9.4	[1]	$ 11.9	[1]

[1] At September 30, 2013, there was $1.4 million of natural gas purchases recorded for these activities.