Supplemental Cash Flow Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
NON-CASH INVESTING AND FINANCING ACTIVITIES
Installment payments for Tinker electric distribution system	$ 0		$ 10.6		$ 0
Power plant long-term service agreement	9.7		0		1.7
Investment in Enable	1,248.6		0		0
SUPPLEMENTAL CASH FLOW INFORMATION
Interest (net of interest capitalized)	151.1	[1]	161.3	[1]	138.9	[1]
Income taxes (net of income tax refunds)	(1.1)		(9.1)		4.7
Interest costs capitalized	$ 5.4		$ 8.0		$ 19.1

[1] Net of interest capitalized of $5.4 million, $8.0 million and $19.1 million in 2013, 2012 and 2011, respectively.