Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Total long-term debt	$ 2,848.6	$ 2,737.1
Percent of Principal Amount Subject to Optional Tender	100.00%
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	0.2
Long-term Debt, Maturities, Repayments of Principal in Year Two	300.2
Long-term Debt, Maturities, Repayments of Principal in Year Three	250.2
Long-term Debt, Maturities, Repayments of Principal in Year Four	110.2
Long-term Debt, Maturities, Repayments of Principal in Year Five	125.2
Garfield Industrial Authority, January 1, 2025 [Member]
Debt Instrument [Line Items]
Date Due	Jan. 01, 2025
Muskogee Industrial Authority, Janaury 1, 2025 [Member]
Debt Instrument [Line Items]
Date Due	Jan. 01, 2025
Muskogee Industrial Authority, June 1, 2027 [Member]
Debt Instrument [Line Items]
Date Due	Jun. 01, 2027
Redeemable during the next 12 months
Debt Instrument [Line Items]
Total long-term debt	135.4
Redeemable during the next 12 months \| Garfield Industrial Authority, January 1, 2025 [Member]
Debt Instrument [Line Items]
Series Minimum	0.22%
Series Maximum	0.40%
Redeemable during the next 12 months \| Muskogee Industrial Authority, Janaury 1, 2025 [Member]
Debt Instrument [Line Items]
Series Minimum	0.21%
Series Maximum	0.41%
Redeemable during the next 12 months \| Muskogee Industrial Authority, June 1, 2027 [Member]
Debt Instrument [Line Items]
Series Minimum	0.20%
Series Maximum	0.47%
OG&E [Member] \| Redeemable during the next 12 months \| Garfield Industrial Authority, January 1, 2025 [Member]
Debt Instrument [Line Items]
Long term debt, gross	47.0	47.0
OG&E [Member] \| Redeemable during the next 12 months \| Muskogee Industrial Authority, Janaury 1, 2025 [Member]
Debt Instrument [Line Items]
Long term debt, gross	32.4	32.4
OG&E [Member] \| Redeemable during the next 12 months \| Muskogee Industrial Authority, June 1, 2027 [Member]
Debt Instrument [Line Items]
Long term debt, gross	56.0	56.0
Enogex LLC Term Loan [Member]
Debt Instrument [Line Items]
Long term debt, gross	250.0
Senior Notes [Member] \| Enogex LLC [Member] \| Series Due August 2, 2015 [Member]
Debt Instrument [Line Items]
Long term debt, gross	$ 250.0	$ 0
Date Due	Aug. 02, 2015

Percent of Principal Amount Subject to Optional Tender

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- Definition

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

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- Definition

When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date.

+ References

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year.

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Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year.

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Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year.

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Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year.

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Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year.

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