Related-Party Transactions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Related Party Transaction [Line Items]
Dividends, Common Stock	$ 170.0	$ 75.0
Operating Costs Charged [Member] | Og and E [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	120.1	118.4	129.7
Og and E [Member] | Enogex [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	10.2	12.4	8.1
Og and E [Member] | Natural Gas Transportation [Member] | Enogex [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	34.8	34.8	34.8
Og and E [Member] | Natural Gas Storage [Member] | Enogex [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	12.9	12.9	12.7
Og and E [Member] | Natural Gas Purchases [Member] | Enogex [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	22.4	20.4	34.7
Retained Earnings [Member]
Related Party Transaction [Line Items]
Dividends, Common Stock	(170.0)	(75.0)
Additional Paid-in Capital [Member]
Related Party Transaction [Line Items]
Dividends, Common Stock	$ 0	$ 0