Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis [Table Text Block]

The following tables summarize the Company's assets and liabilities that are measured at fair value on a recurring basis at March 31, 2013 and December 31, 2012 as well as reconcile the Company's commodity contracts fair value to PRM Assets and Liabilities on the Company's Condensed Consolidated Balance Sheets at March 31, 2013 and December 31, 2012. The Company adopted the Financial Accounting Standards Board accounting guidance requiring additional disclosures for balance sheet offsetting of assets and liabilities effective January 1, 2013. The Company posted $0.1 million and $0.2 million of collateral at March 31, 2013 and December 31, 2012, respectively, which has been included within netting adjustments in the table below. The Company held no collateral at March 31, 2013 or December 31, 2012. The Company has offset all amounts subject to master netting agreements in the Company's Condensed Consolidated Balance Sheets at March 31, 2013 and December 31, 2012. The Company held no Level 1 investments at March 31, 2013 and no Level 3 investments at March 31, 2013 or December 31, 2012.

March 31, 2013
(In millions)	Commodity Contracts						Gas Imbalances (A)
	Assets			Liabilities			Assets (B)		Liabilities (C)
Significant other observable inputs (Level 2)	$	0.5		$	0.6		$	4.2	$	4.8
Total fair value	0.5			0.6			4.2		4.8
Netting adjustments	(0.1		)	(0.2		)	—		—
Total	$	0.4		$	0.4		$	4.2	$	4.8
December 31, 2012
(In millions)	Commodity Contracts						Gas Imbalances (A)
	Assets			Liabilities			Assets (B)		Liabilities (C)
Quoted market prices in active market for identical assets (Level 1)	$	5.0		$	5.0		$	—	$	—
Significant other observable inputs (Level 2)	0.5			0.5			3.1		3.8
Total fair value	5.5			5.5			3.1		3.8
Netting adjustments	(5.0		)	(5.2		)	—		—
Total	$	0.5		$	0.3		$	3.1	$	3.8

(A) The Company uses the market approach to fair value its gas imbalance assets and liabilities, using an average of the Inside FERC Gas Market Report for Panhandle Eastern Pipe Line Co. (Texas, Oklahoma Mainline), ONEOK (Oklahoma) and ANR Pipeline (Oklahoma) indices.

(B) Gas imbalance assets exclude fuel reserves for under retained fuel due from shippers of $8.5 million and $5.9 million at March 31, 2013 and December 31, 2012, respectively, which fuel reserves are based on the value of natural gas at the time the imbalance was created and which are not subject to revaluation at fair market value.

(C) Gas imbalance liabilities exclude fuel reserves for over retained fuel due to shippers of $1.1 million and $1.2 million at March 31, 2013 and December 31, 2012, respectively, which fuel reserves are based on the value of natural gas at the time the imbalance was created and which are not subject to revaluation at fair market value.

Schedule of Fair Value and Carrying Amount of PRM Financial Instruments [Table Text Block]

The following table summarizes the fair value and carrying amount of the Company's financial instruments, including derivative contracts related to the Company's PRM activities, atMarch 31, 2013 and December 31, 2012.

	March 31, 2013				December 31, 2012
(In millions)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
PRM Assets
Energy Derivative Contracts	$	0.4	$	0.4	$	0.5	$	0.5
PRM Liabilities
Energy Derivative Contracts	$	0.4	$	0.4	$	0.3	$	0.3
Long-Term Debt
OG&E Senior Notes	$	1,904.3	$	2,368.3	$	1,904.2	$	2,401.6
OG&E Industrial Authority Bonds	135.4		135.4		135.4		135.4
OG&E Tinker Debt	10.6		10.3		10.7		10.0
OGE Energy Senior Notes	99.9		105.6		99.9		106.3
Enogex LLC Senior Notes	448.5		492.1		448.4		493.4
Enogex LLC Term Loan	250.0		250.0		250.0		250.0