Retirement Plans and Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net Periodic Benefit Cost	$ 7.6		$ 7.5		$ 15.3		$ 14.9
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	4.5		4.4		9.0		8.8
Interest cost	7.5		8.3		15.0		16.6
Expected return on plan assets	(11.5)		(11.3)		(23.0)		(22.7)
Amortization of net loss	6.0		4.8		11.9		9.6
Amortization of unrecognized prior service cost	0.5	[1]	0.6	[1]	1.1	[1]	1.2	[1]
Net Periodic Benefit Cost	7.0	[2]	6.8	[2]	14.0	[3]	13.5	[3]
Restoration of Retirement Income Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.2		0.2		0.5		0.5
Interest cost	0.2		0.2		0.3		0.3
Expected return on plan assets	0		0		0		0
Amortization of net loss	0.1		0.1		0.2		0.2
Amortization of unrecognized prior service cost	0.1	[1]	0.2	[1]	0.3	[1]	0.4	[1]
Net Periodic Benefit Cost	0.6	[2]	0.7	[2]	1.3	[3]	1.4	[3]
Postretirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	1.1		0.9		2.1		1.8
Interest cost	3.0		3.1		6.0		6.2
Expected return on plan assets	(0.7)		(1.3)		(1.5)		(2.6)
Amortization of transition obligation	0.7		0.7		1.4		1.4
Amortization of net loss	5.1		4.5		10.2		9.1
Amortization of unrecognized prior service cost	(4.2)	[1]	(4.1)	[1]	(8.3)	[1]	(8.2)	[1]
Net Periodic Benefit Cost	5.0	[4]	3.8	[4]	9.9	[5]	7.7	[5]
OKLAHOMA | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Additional Pension Expense to Meet State Requirements	2.8		2.8		5.7		5.3
OKLAHOMA | Postretirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Increase in Postretirement Medical Expense	$ 0.4		$ 1.7		$ 0.8		$ 1.7

[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 $7.6 million and $7.5 million of net periodic benefit cost recognized by the Company during the three months ended June 30, 2012 and 2011, respectively, OG&E recognized an increase in pension expense during each of the three months ended June 30, 2012 and 2011 of $2.8 million 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 $15.3 million and $14.9 million of net periodic benefit cost recognized by the Company during the six months ended June 30, 2012 and 2011, respectively, OG&E recognized an increase in pension expense during the six months ended June 30, 2012 and 2011 of $5.7 million and $5.3 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).

[4] In addition to the $5.0 million and $3.8 million of net periodic benefit cost recognized by the Company during the three months ended June 30, 2012 and 2011, respectively, OG&E recognized an increase in postretirement medical expense during the three months ended June 30, 2012 and 2011, of $0.4 million and $1.7 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).

[5] In addition to the $9.9 million and $7.7 million of net periodic benefit cost recognized by the Company during the six months ended June 30, 2012 and 2011, respectively, OG&E recognized an increase in postretirement medical expense during the six months ended June 30, 2012 and 2011, of $0.8 million and $1.7 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).