Summary of Significant Accounting Policies Accounting Records (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Components of Benefit Obligation Regulatory Asset	$ 227.4	$ 370.6
Components of Net Periodic Benefit Costs to be Recognized in Next Fiscal Year	(1.0)
Smart Grid Project [Member]
Smart Grid Cost Cap	366.4
U.S. Department of Energy Funds	130.0
Operations and Maintenance Expenses [Member]
Deferred Storm and Property Reserve Deficiency, Current	2.7
Regulatory Asset [Member]
Components of Net Periodic Benefit Costs to be Recognized in Next Fiscal Year	10.7
Pension Plans, Defined Benefit [Member] | Defined Benefit Plans Income Loss [Member]
Components of Benefit Obligation Regulatory Asset	178.4	278.6
Components of Net Periodic Benefit Costs to be Recognized in Next Fiscal Year	11.4
Pension Plans, Defined Benefit [Member] | Prior Service Cost [Member]
Components of Benefit Obligation Regulatory Asset	2.5	4.5
Components of Net Periodic Benefit Costs to be Recognized in Next Fiscal Year	2.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Defined Benefit Plans Income Loss [Member]
Components of Benefit Obligation Regulatory Asset	79.9	134.6
Components of Net Periodic Benefit Costs to be Recognized in Next Fiscal Year	11.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Prior Service Cost [Member]
Components of Benefit Obligation Regulatory Asset	(33.4)	(47.1)
Components of Net Periodic Benefit Costs to be Recognized in Next Fiscal Year	(13.7)
OKLAHOMA | Web Portal Access and Education [Member] | Smart Grid Project [Member]
Smart Grid Costs to be Recovered	$ 6.9