Summary of Significant Accounting Policies Asset Retirement Obligation (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at January 1	$ 54.0		$ 24.8
Liabilities settled	(0.4)	[1]	0
Accretion expense	1.1		0.9
Revisions in estimated cash flows	0		26.7	[2]
Balance at June 30	54.7		52.4
OGE Enogex Holdings [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at June 30	$ 0

[1] As a result of the formation of Enable Midstream Partners on May 1, 2013, the Company has no obligations at June 30, 2013 under OGE Holdings' asset retirement obligations previously disclosed in the Company's 2012 10-K.

[2] Due to changes to OG&E's asset retirement obligations related to its wind farms as a result of changes in the assumption related to the timing of removal used in the valuation of the asset retirement obligations.