Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended					6 Months Ended						6 Months Ended	3 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Jun. 30, 2014 Garfield Industrial Authority Bond [Member]	Jun. 30, 2014 Muskogee Industrial Authority Bond Due 2025 [Member]	Jun. 30, 2014 Muskogee Industrial Authority Bond Due 2027 [Member]	Jun. 30, 2014 Redeemable during the next 12 months	Jun. 30, 2014 Redeemable during the next 12 months Garfield Industrial Authority Bond [Member]	Jun. 30, 2014 Redeemable during the next 12 months Muskogee Industrial Authority Bond Due 2025 [Member]	Jun. 30, 2014 Redeemable during the next 12 months Muskogee Industrial Authority Bond Due 2027 [Member]	Jun. 30, 2014 OG&E [Member] Redeemable during the next 12 months Garfield Industrial Authority Bond [Member]	Jun. 30, 2014 OG&E [Member] Redeemable during the next 12 months Muskogee Industrial Authority Bond Due 2025 [Member]	Jun. 30, 2014 OG&E [Member] Redeemable during the next 12 months Muskogee Industrial Authority Bond Due 2027 [Member]	Jun. 30, 2014 Senior Notes [Member] OG&E [Member] Series due May 1, 2043 [Member]	Sep. 30, 2014 Senior Notes [Member] OG&E [Member] Series Due August 1, 2034 [Member]	Aug. 01, 2014 Senior Notes [Member] OG&E [Member] Series Due August 1, 2034 [Member]
Debt Instrument [Line Items]
Series Minimum							0.15%	0.08%	0.08%
Series Maximum							0.20%	0.18%	0.11%
Long term debt, gross										$ 47.0	$ 32.4	$ 56.0	$ 250.0		$ 140.0
Debt Instrument, Interest Rate, Stated Percentage													4.55%		6.50%
Long-term debt						135.4
Date Due			Jan. 01, 2025	Jan. 01, 2025	Jun. 01, 2027								Mar. 15, 2044	Aug. 01, 2034
Percent of Principal Amount Subject to Optional Tender		100.00%
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed														103.25%
Redemption Premium	$ 4.6