Retirement Plans and Postretirement Benefit Plans Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	$ 61.4		$ 59.6
Plan investments attributable to affiliates	(4.7)		(4.1)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Level 3 Asset Value, Beginning of Period	53.3
Unrealized Gains	(0.5)
Interest Income	1.1
Dividend Income	0.6
Realized Gains	0.4
Administrative Expenses and Charges	(0.1)
Claims Paid	(1.7)
Level 3 Asset Value, End of Period	53.1
Postretirement Plan, Expected Future Benefit Payments in Year One	13.1
Postretirement Plan, Expected Future Benefit Payments in Year Two	13.5
Postretirement Plan, Expected Future Benefit Payments in Year Three	13.8
Postretirement Plan, Expected Future Benefit Payments in Year Four	14.0
Postretirement Plan, Expected Future Benefit Payments in Year Five	14.3
Postretirement Plan, Expected Future Benefit Payments Thereafter	71.6
Postemployment Benefits Liability	1.4		2.2
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	8.3		6.3
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	53.1		53.3
OG&E [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	56.7		55.5
Group Retiree Medical Insurance Contract [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	53.1	[1]	53.3	[1]
Group Retiree Medical Insurance Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	0	[1]	0	[1]
Group Retiree Medical Insurance Contract [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	53.1	[1]	53.3	[1]
U.S. Equity Mutual Funds Investment [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	7.9		6.0
U.S. Equity Mutual Funds Investment [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	7.9		6.0
U.S. Equity Mutual Funds Investment [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	0		0
Money Market Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	0.4		0.3
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	0.4		0.3
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	0		0
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit Obligation	(202.4)		(236.4)
Fair Value of Plan Assets	56.7		55.5
Funded Status of Plan	(145.7)		(180.9)
Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit Obligation	(202.4)		(236.4)		(223.1)
Fair Value of Plan Assets	56.7		55.5		57.2
Funded Status of Plan	(145.7)		(180.9)
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year	8.35%		8.55%		8.75%
Postretirement Benefit Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	$ 0		$ 0

[1] This category represents a group retiree medical insurance contract which invests in a pool of common stocks, bonds and money market accounts, of which a significant portion is comprised of mortgage-backed securities.