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Retirement Plans and Postretirement Benefit Plans (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined Contribution Plan, Cost Recognized   $ 7.8 $ 7.6 $ 7.0
Estimated Future Employer Contributions in Next Fiscal Year 26.0      
Fair Value of Plan Assets 61.4 59.6    
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months 75.4      
Defined Benefit Plan, Expected Future Benefit Payments, Year Two 65.1      
Defined Benefit Plan, Expected Future Benefit Payments, Year Three 59.9      
Defined Benefit Plan, Expected Future Benefit Payments, Year Four 53.1      
Defined Benefit Plan, Expected Future Benefit Payments, Year Five 49.1      
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter 183.3      
Effect of One Percentage Point Increase on Service and Interest Cost Components 0 0 0  
Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation 0.1 0.1 0.1  
Effect of One Percentage Point Decrease on Service and Interest Cost Components 0 0.1 0.1  
Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation 0.4 0.7 0.4  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Beginning 59.6      
Fair Value of Plan Assets, Ending 61.4 59.6    
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]        
Defined Benefit Plan, Contributions by Employer 35.0 35.0    
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    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 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    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 53.1 53.3    
U.S. common stocks [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 236.8 232.2    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 236.8 232.2    
U.S. common stocks [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 236.8 232.2    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 236.8 232.2    
U.S. common stocks [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    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 0    
Foreign common stocks [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 39.3 39.9    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 39.3 39.9    
Foreign common stocks [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 39.3 39.9    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 39.3 39.9    
Foreign common stocks [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    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 0    
U.S. treasury notes and bonds [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 159.8 [1] 138.6 [1]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 159.8 [1] 138.6 [1]    
U.S. treasury notes and bonds [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 159.8 [1] 138.6 [1]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 159.8 [1] 138.6 [1]    
U.S. treasury notes and bonds [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 [1] 0 [1]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 [1] 0 [1]    
Mortgage-backed Securities [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 50.3 55.8    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 50.3 55.8    
Mortgage-backed Securities [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 0    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 0    
Mortgage-backed Securities [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 50.3 55.8    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 50.3 55.8    
Corporate fixed income and other securities [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 110.6 [2] 98.4 [2]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 110.6 [2] 98.4 [2]    
Corporate fixed income and other securities [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 [2] 0 [2]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 [2] 0 [2]    
Corporate fixed income and other securities [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 110.6 [2] 98.4 [2]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 110.6 [2] 98.4 [2]    
Mortgage-backed securities [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 22.3 [2] 13.5 [2]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 22.3 [2] 13.5 [2]    
Mortgage-backed securities [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 [2] 0 [2]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 [2] 0 [2]    
Mortgage-backed securities [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 22.3 [2] 13.5 [2]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 22.3 [2] 13.5 [2]    
Commingled fund [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 29.2 [3] 34.9 [3]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 29.2 [3] 34.9 [3]    
Commingled fund [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 [3] 0 [3]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 [3] 0 [3]    
Commingled fund [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 29.2 [3] 34.9 [3]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 29.2 [3] 34.9 [3]    
Common/collective trust [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 26.0 [4] 25.6 [4]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 26.0 [4] 25.6 [4]    
Common/collective trust [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 [4]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 [4] 0 [4]    
Common/collective trust [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 26.0 [4] 25.6 [4]    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 26.0 [4] 25.6 [4]    
Foreign government bonds [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 4.0 3.9    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 4.0 3.9    
Foreign government bonds [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 0    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 0    
Foreign government bonds [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 4.0 3.9    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 4.0 3.9    
U.S. municipal bonds [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 2.0 0.8    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 2.0 0.8    
U.S. municipal bonds [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 0    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 0    
U.S. municipal bonds [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 2.0 0.8    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 2.0 0.8    
Interest-bearing cash [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 0.1 0.2    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0.1 0.2    
Interest-bearing cash [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 0.2    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0.1 0.2    
Interest-bearing cash [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    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 0    
Receivable (foreign currency) [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 1.1 0.4    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 1.1 0.4    
Receivable (foreign currency) [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 0    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 0    
Receivable (foreign currency) [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 1.1 0.4    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 1.1 0.4    
Payable (foreign currency) [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets (1.1) (0.4)    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending (1.1) (0.4)    
Payable (foreign currency) [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 0    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 0    
Payable (foreign currency) [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 (1.1) (0.4)    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending (1.1) (0.4)    
Total Plan investments [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 680.4 643.8    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 680.4 643.8    
Total Plan investments [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 436.0 410.9    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 436.0 410.9    
Total Plan investments [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 244.4 232.9    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 244.4 232.9    
Receivable from broker for securities sold [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 11.5 0.8    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 11.5 0.8    
Interest and dividends receivable [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 3.2 2.8    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 3.2 2.8    
Payable to broker for securities purchased [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets (40.2) (21.4)    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending (40.2) (21.4)    
Plan investments attributable to affiliates [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets (138.4) (107.0)    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending (138.4) (107.0)    
Total Plan assets [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 516.5 519.0    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 516.5 519.0    
Pension Plan [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Settlements 17.6      
Fair Value of Plan Assets 516.5 519.0 485.9  
Funded Status of Plan 12.9 (55.6)    
Accumulated Benefit Obligation 483.0 549.3    
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]        
Benefit Obligation, Beginning (574.6) (546.9)    
Service cost (11.6) (10.9) (10.8)  
Interest cost (20.4) (23.5) (26.2)  
Participants' contributions 49.9 0    
Medicare subsidies received 0 0    
Actuarial gains (losses) 39.8 (43.7)    
Benefits paid 13.3 50.4    
Benefit Obligation, Ending (503.6) (574.6) (546.9)  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Beginning 519.0 485.9    
Actual return on plans' assets 60.7 50.5    
Participants' contributions (49.9) 0    
Medicare subsidies received 0 0    
Benefits paid (13.3) (50.4)    
Fair Value of Plan Assets, Ending 516.5 519.0 485.9  
Funded Status of Plan 12.9 (55.6)    
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]        
Service cost 11.6 10.9 10.8  
Interest cost 20.4 23.5 26.2  
Expected return on plan assets (38.9) (38.2) (37.3)  
Amortization of transition obligation 0 0 0  
Amortization of net loss 20.7 19.3 15.6  
Amortization of unrecognized prior service cost 1.9 [5] 2.2 [5] 2.5 [5]  
Settlement 17.6 0 0  
Net Periodic Benefit Cost 33.3 [6] 17.7 [6] 17.8 [6]  
Assumptions Used Calculating Benefit Obligation, Discount Rate 4.60% 3.70% 4.50%  
Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets 8.00% 8.00% 8.00%  
Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase 4.20% 4.20% 4.40%  
Defined Benefit Plan, Contributions by Employer 0 33.0    
Pension Plan [Member] | OKLAHOMA
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Settlements 17.0      
Pension Plan [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  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending   0 0  
Restoration of Retirement Income Plan [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 0 0 0  
Funded Status of Plan (2.1) (2.2)    
Accumulated Benefit Obligation 1.9 2.1    
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]        
Benefit Obligation, Beginning (2.2) (2.2)    
Service cost (0.1) (0.1) (0.1)  
Interest cost (0.1) (0.1) (0.1)  
Participants' contributions 0 0    
Medicare subsidies received 0 0    
Actuarial gains (losses) 0.2 (0.4)    
Benefits paid 0.1 0.6    
Benefit Obligation, Ending (2.1) (2.2) (2.2)  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Beginning 0 0    
Actual return on plans' assets 0 0    
Participants' contributions 0 0    
Medicare subsidies received 0 0    
Benefits paid (0.1) (0.6)    
Fair Value of Plan Assets, Ending 0 0 0  
Funded Status of Plan (2.1) (2.2)    
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]        
Service cost 0.1 0.1 0.1  
Interest cost 0.1 0.1 0.1  
Expected return on plan assets 0 0 0  
Amortization of transition obligation 0 0 0  
Amortization of net loss 0 0.1 0.1  
Amortization of unrecognized prior service cost 0.1 [5] 0.2 [5] 0.2 [5]  
Settlement 0 0.3 0  
Net Periodic Benefit Cost 0.3 [6] 0.8 [6] 0.5 [6]  
Defined Benefit Plan, Contributions by Employer 0.1 0.6    
Pension Plans [Member]
       
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]        
Net Periodic Benefit Cost 46.7 34.1 30.2  
Capitalized Portion of Net Periodic Benefit Cost 4.2 5.5 5.3  
Pension Plans [Member] | OKLAHOMA
       
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]        
Additional Pension Expense to Meet State Requirements 5.8 8.3 10.8  
Postretirement Benefit Plan [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Fair Value of Plan Assets 56.7 55.5 57.2  
Funded Status of Plan (145.7) (180.9)    
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]        
Benefit Obligation, Beginning (236.4) (223.1)    
Service cost (2.9) (2.7) (2.4)  
Interest cost (8.1) (9.4) (10.0)  
Participants' contributions (2.5) (2.5)    
Medicare subsidies received 0 (0.5)    
Actuarial gains (losses) 35.4 (9.4)    
Benefits paid 12.1 11.2    
Benefit Obligation, Ending (202.4) (236.4) (223.1)  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Beginning 55.5 57.2    
Actual return on plans' assets 3.4 4.3    
Participants' contributions 2.5 2.5    
Medicare subsidies received 0 0.5    
Benefits paid (12.1) (11.2)    
Fair Value of Plan Assets, Ending 56.7 55.5 57.2  
Funded Status of Plan (145.7) (180.9)    
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]        
Service cost 2.9 2.7 2.4  
Interest cost 8.1 9.4 10.0  
Expected return on plan assets (2.4) (2.8) (4.9)  
Amortization of transition obligation 0 2.5 2.6  
Amortization of net loss 18.2 17.4 15.5  
Amortization of unrecognized prior service cost (13.7) [5] (13.6) [5] (13.7) [5]  
Settlement 0 0 0  
Net Periodic Benefit Cost 13.1 [6] 15.6 [6] 11.9 [6]  
Capitalized Portion of Net Periodic Benefit Cost 3.4 4.7 3.3  
Assumptions Used Calculating Benefit Obligation, Discount Rate 4.60% 3.60% 4.50%  
Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets 4.00% 4.00% 6.50%  
Health Care Cost Trend Rate Assumed for Next Fiscal Year 8.35% 8.55% 8.75%  
Ultimate Health Care Cost Trend Rate 4.48% 4.48% 4.48%  
Year that Rate Reaches Ultimate Trend Rate 2028 2028 2028  
Defined Benefit Plan, Contributions by Employer 7.4 2.2    
Postretirement Benefit Plan [Member] | OKLAHOMA
       
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]        
Additional Postretirement Medical Expense to Meet State Requirements 0.6 0.8    
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    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Ending 0 0    
Less Than 90% [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Projected Benefit Obligation Funded Status Thresholds Fixed Income 50.00%      
Projected Benefit Obligation Funded Status Thresholds Equity 50.00%      
Projected Benefit Obligation Funded Status Thresholds 100.00%      
95% [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Projected Benefit Obligation Funded Status Thresholds Fixed Income 58.00%      
Projected Benefit Obligation Funded Status Thresholds Equity 42.00%      
Projected Benefit Obligation Funded Status Thresholds 100.00%      
100% [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Projected Benefit Obligation Funded Status Thresholds Fixed Income 65.00%      
Projected Benefit Obligation Funded Status Thresholds Equity 35.00%      
Projected Benefit Obligation Funded Status Thresholds 100.00%      
105% [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Projected Benefit Obligation Funded Status Thresholds Fixed Income 73.00%      
Projected Benefit Obligation Funded Status Thresholds Equity 27.00%      
Projected Benefit Obligation Funded Status Thresholds 100.00%      
110% [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Projected Benefit Obligation Funded Status Thresholds Fixed Income 80.00%      
Projected Benefit Obligation Funded Status Thresholds Equity 20.00%      
Projected Benefit Obligation Funded Status Thresholds 100.00%      
115% [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Projected Benefit Obligation Funded Status Thresholds Fixed Income 85.00%      
Projected Benefit Obligation Funded Status Thresholds Equity 15.00%      
Projected Benefit Obligation Funded Status Thresholds 100.00%      
120% [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Projected Benefit Obligation Funded Status Thresholds Fixed Income 90.00%      
Projected Benefit Obligation Funded Status Thresholds Equity 10.00%      
Projected Benefit Obligation Funded Status Thresholds 100.00%      
Domestic All-Cap/Large Cap Equity [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Target Plan Asset Allocations 50.00%      
Target Plan Asset Allocations Range Minimum 50.00%      
Target Plan Asset Allocations Range Maximum 60.00%      
Domestic Mid-Cap Equity [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Target Plan Asset Allocations 15.00%      
Target Plan Asset Allocations Range Minimum 5.00%      
Target Plan Asset Allocations Range Maximum 25.00%      
Domestic Small-Cap Equity [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Target Plan Asset Allocations 15.00%      
Target Plan Asset Allocations Range Minimum 5.00%      
Target Plan Asset Allocations Range Maximum 25.00%      
International Equity [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Target Plan Asset Allocations 20.00%      
Target Plan Asset Allocations Range Minimum 10.00%      
Target Plan Asset Allocations Range Maximum 30.00%      
OG&E [Member]
       
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Pension Contributions   0 33.0  
Estimated Future Employer Contributions in Next Fiscal Year 1.0      
Fair Value of Plan Assets 56.7 55.5    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]        
Fair Value of Plan Assets, Beginning 55.5      
Fair Value of Plan Assets, Ending $ 56.7 $ 55.5    
[1] This category represents U.S. treasury notes and bonds with a Moody's Investors Services rating of Aaa and Government Agency Bonds with a Moody's Investors Services rating of A1 or higher.
[2] This category primarily represents U.S. corporate bonds with an investment grade rating at or above Baa3 or BBB- by Moody's Investors Services, Standard & Poor's Ratings Services or Fitch Ratings.
[3] This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets.
[4] This category represents units of participation in an investment pool which primarily invests in foreign or domestic bonds, debentures, mortgages, equipment or other trust certificates, notes, obligations issued or guaranteed by the U.S. Government or its agencies, bank certificates of deposit, bankers' acceptances and repurchase agreements, high grade commercial paper and other instruments with money market characteristics with a fixed or variable interest rate. There are no restrictions on redemptions in the common/collective trust.
[5] 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.
[6] In addition to the $46.7 million, $34.1 million and $30.2 million of net periodic benefit cost recognized in 2013, 2012 and 2011, respectively, OG&E recognized the following: •an increase in pension expense in 2013, 2012 and 2011 of $5.8 million, $8.3 million and $10.8 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 asset or liability (see Note 1); and•an increase in postretirement medical expense in 2013 and 2012 of $0.6 million and $0.8 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 asset or liability (see Note 1);•a deferral of pension expense in 2013 of $17.0 million which includes a portion of OGE Energy's pension settlement charge, related to the pension settlement charge of $17.6 million which is included in the Pension tracker regulatory account (see Note 1).