Short-Term Debt and Credit Facilities (Details) (USD $) In Millions, unless otherwise specified			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Og and E [Member]	Mar. 31, 2013 Maximum [Member]	Mar. 31, 2013 Commercial Paper [Member] Og and E [Member]	Mar. 31, 2013 Letter of Credit [Member] Og and E [Member]
Short-term Debt [Line Items]
Advances from parent	$ 54.4	$ 0
Advances to parent	0	90.3
Intercomany Borrowings, Maximum Borrowing Capacity			400.0
Line of Credit Facility, Expiration Date			Dec. 13, 2016
Outstanding Intercompany Borrowings			41.4
Aggregate Commitment - Revolving Credit Facility			400.0
Letters of Credit Outstanding			2.1
Weighted Average Interest Rate					0.32%	0.53%
Commercial paper borrowings			43.1
Cash				0.1
Short Term Borrowing Capacity That Has Regulatory Approval			$ 800
Period For Which Regulatory Approval Has Been Given to Acquire Short Term Debt			2 years