Commitments and Contingencies Other Purchase Obligations and Commitments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended								60 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2017
Long-term Purchase Commitment [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months						$ 10.7
Operating Leases, Future Minimum Payments, Due in Two Years						9.4
Operating Leases, Future Minimum Payments, Due in Three Years						9.1
Operating Leases, Future Minimum Payments, Due in Four Years						33.6
Operating Leases, Future Minimum Payments, Due in Five Years						3.9
Operating Leases, Future Minimum Payments, Due Thereafter						51.9
Operating Leases, Future Minimum Payments Due						118.6
Operating Leases, Rent Expense, Net						14.2	10.4	10.3
Long-term Purchase Commitment, Amount	234.6	230.2	490.1	501.2	628.9				2,085.0
Utilities Operating Expense, Purchased Power under Long-term Contracts						49.5	36.7	7.7
Enogex Building Lease [Member]
Long-term Purchase Commitment [Line Items]
Operating Leases, Future Minimum Payments Due						11.3
Public Utility Regulatory Policy Act of 1978 [Member]
Long-term Purchase Commitment [Line Items]
Percentage of output purchased						100.00%
OG&E cogeneration capacity and fixed operation and maintenance payments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	80.1	82.4	84.5	85.8	87.9				420.7
OG&E expected cogeneration energy payments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	87.3	81.0	70.5	63.8	58.6				361.2
OG&E minimum fuel purchase commitments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	0	0	264.8	255.0	405.0	585.6	647.6	721.4	924.8
Percentage of OG&E's Projected 2013 Requirements					26.10%
OG&E expected wind purchase commitments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	60.8	59.8	58.9	58.0	57.5				295.0
OG&E long-term service agreement commitments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	6.4	6.2	6.7	27.8	8.0				55.1
EER commitments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	0	0.8	4.7	10.8	11.9				28.2
Initial capacity						60,000
Initial annual demand fee						7.4
Initial capacity turned back						20,000
Firm Capacity						10,000
Annual Demand Fee						2.1
OG&E total cogeneration payments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount						135.1	140.7	147.3
OG&E capacity payments [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount						77.1	78.0	80.7
CPV Keenan [Member]
Long-term Purchase Commitment [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts						25.1	24.5	3.8
Edison Mission Energy [Member]
Long-term Purchase Commitment [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts						20.2	8.5	0
FPL Energy [Member]
Long-term Purchase Commitment [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts						3.4	3.7	3.9
NextEra Energy [Member]
Long-term Purchase Commitment [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts						0.8	0	0
McClain Plant [Member]
Long-term Purchase Commitment [Line Items]
Ownership Interest in McClain Plant						77.00%
Factored-Fired Hours						96,000
Factored-Fired Starts						4,800
Redbud Plant [Member]
Long-term Purchase Commitment [Line Items]
Ownership Interest in Redbud Plant						51.00%
Factored-Fired Hours						120,000
Factored-Fired Starts						4,500
OG&E Railcar Lease Agreement [Member]
Long-term Purchase Commitment [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months						3.2
Operating Leases, Future Minimum Payments, Due in Two Years						2.8
Operating Leases, Future Minimum Payments, Due in Three Years						2.7
Operating Leases, Future Minimum Payments, Due in Four Years						27.3
Operating Leases, Future Minimum Payments, Due in Five Years						0
Operating Leases, Future Minimum Payments, Due Thereafter						0
Operating Leases, Future Minimum Payments Due						36.0
OG&E Wind Farm Land Lease Agreements [Member]
Long-term Purchase Commitment [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months						2.0
Operating Leases, Future Minimum Payments, Due in Two Years						2.1
Operating Leases, Future Minimum Payments, Due in Three Years						2.1
Operating Leases, Future Minimum Payments, Due in Four Years						2.1
Operating Leases, Future Minimum Payments, Due in Five Years						2.4
Operating Leases, Future Minimum Payments, Due Thereafter						51.2
Operating Leases, Future Minimum Payments Due						61.9
OGE Energy Building Lease [Member]
Long-term Purchase Commitment [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months						0.3
Operating Leases, Future Minimum Payments, Due in Two Years						0.8
Operating Leases, Future Minimum Payments, Due in Three Years						0.8
Operating Leases, Future Minimum Payments, Due in Four Years						0.8
Operating Leases, Future Minimum Payments, Due in Five Years						0.8
Operating Leases, Future Minimum Payments, Due Thereafter						0.7
Operating Leases, Future Minimum Payments Due						4.2
Enogex Noncancellable Operating Leases [Member]
Long-term Purchase Commitment [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months						5.2
Operating Leases, Future Minimum Payments, Due in Two Years						3.7
Operating Leases, Future Minimum Payments, Due in Three Years						3.5
Operating Leases, Future Minimum Payments, Due in Four Years						3.4
Operating Leases, Future Minimum Payments, Due in Five Years						0.7
Operating Leases, Future Minimum Payments, Due Thereafter						0
Operating Leases, Future Minimum Payments Due						$ 16.5