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	$ 3.4		$ 4.5
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	3.1		2.7
Interest cost	5.0		5.9
Expected return on plan assets	(10.2)		(9.5)
Amortization of net loss	4.9		4.8
Amortization of unrecognized prior service cost	0.5	[1]	0.5	[1]
Net Periodic Benefit Cost	3.3	[2]	4.4	[2]
Restoration of Retirement Income Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0		0
Interest cost	0		0
Expected return on plan assets	0		0
Amortization of net loss	0		0
Amortization of unrecognized prior service cost	0.1	[1]	0.1	[1]
Net Periodic Benefit Cost	0.1	[2]	0.1	[2]
Postretirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.8		0.7
Interest cost	2.1		2.4
Expected return on plan assets	(0.6)		(0.7)
Amortization of transition obligation	0		0.6
Amortization of net loss	4.5		4.3
Amortization of unrecognized prior service cost	(3.4)	[1]	(3.4)	[1]
Net Periodic Benefit Cost	3.4	[3]	3.9	[3]
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 Plans [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 $3.4 million and $4.5 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 $3.4 million and $3.9 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).