Retirement Plans and Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net Periodic Benefit Cost	$ 6.6		$ 7.7
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	5.0		4.5
Interest cost	6.6		7.5
Expected return on plan assets	(12.3)		(11.5)
Amortization of net loss	6.2		5.9
Amortization of unrecognized prior service cost	0.5	[1]	0.6	[1]
Net Periodic Benefit Cost	6.0	[2]	7.0	[2]
Capitalized Portion of Net Periodic Benefit Cost	1.1		1.5
Restoration of Retirement Income Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.3		0.3
Interest cost	0.1		0.1
Expected return on plan assets	0		0
Amortization of net loss	0.1		0.1
Amortization of unrecognized prior service cost	0.1	[1]	0.2	[1]
Net Periodic Benefit Cost	0.6	[2]	0.7	[2]
Postretirement Benefit Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	1.2		1.0
Interest cost	2.6		3.0
Expected return on plan assets	(0.6)		(0.8)
Amortization of transition obligation	0		0.7
Amortization of net loss	5.3		5.1
Amortization of unrecognized prior service cost	(4.1)	[1]	(4.1)	[1]
Net Periodic Benefit Cost	4.4	[3]	4.9	[3]
Capitalized Portion of Net Periodic Benefit Cost	0.8		1.0
OKLAHOMA | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Additional Pension Expense to Meet State Requirements	1.9		2.9
OKLAHOMA | Postretirement Benefit Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Additional Pension Expense to Meet State Requirements	$ 0.1		$ 0.4

[1] Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment.

[2] In addition to the $6.6 million and $7.7 million of net periodic benefit cost recognized during the three months ended March 31, 2013 and 2012, respectively, OG&E recognized an increase in pension expense during the three months ended March 31, 2013 and 2012 of $1.9 million and $2.9 million, respectively, to maintain the allowable amount to be recovered for pension expense in the Oklahoma jurisdiction which are included in the Pension tracker regulatory liability (see Note 1).

[3] In addition to the $4.4 million and $4.9 million of net periodic benefit cost recognized during the three months ended March 31, 2013 and 2012, respectively, OG&E recognized an increase in postretirement medical expense during the three months ended March 31, 2013 and 2012 of $0.1 million and $0.4 million, respectively, to maintain the allowable amount to be recovered for postretirement medical expense in the Oklahoma jurisdiction which are included in the Pension tracker regulatory liability (see Note 1).