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Pension and Other Postretirement Benefits (Schedule Of Fair Value Of Pension Plan Assets) (Details) - USD ($)
$ in Millions
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   $ 480.4  
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount $ 432.0    
Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 1,032.3 934.4  
Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Fair Value, Inputs, Level 1, 2 and 3      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 2,275.4 2,404.1  
Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items 1,975.5 2,110.7  
Pension Plan | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items   231.1  
Pension Plan | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items 177.3    
Pension Plan | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items 1,033.8 936.0  
Pension Plan | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items 0.0 0.0  
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 1,981.7 2,117.7 $ 2,080.9
Pension Plan | Cash [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 10.3 11.9  
Pension Plan | Cash [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   11.9  
Pension Plan | Cash [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 9.7    
Pension Plan | Cash [Member] | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.6 0.0  
Pension Plan | Cash [Member] | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | International Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 150.9 230.1  
Pension Plan | Fixed Income      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 1,382.3 1,291.2  
Pension Plan | Equity Securities [Member] | International Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.5    
Pension Plan | Equity Securities [Member] | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.5    
Pension Plan | Equity Securities [Member] | International Equities | Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Equity Securities [Member] | International Equities | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Equity Securities [Member] | United States Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   2.4  
Pension Plan | Equity Securities [Member] | United States Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   2.4  
Pension Plan | Equity Securities [Member] | United States Equities | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Equity Securities [Member] | United States Equities | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Fixed Income Securities [Member] | Government      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 387.3 243.4  
Pension Plan | Fixed Income Securities [Member] | Government | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Fixed Income Securities [Member] | Government | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Fixed Income Securities [Member] | Government | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 387.3 243.4  
Pension Plan | Fixed Income Securities [Member] | Government | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Fixed Income Securities [Member] | Corporate/Other debt securities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 645.9 692.6  
Pension Plan | Fixed Income Securities [Member] | Corporate/Other debt securities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Fixed Income Securities [Member] | Corporate/Other debt securities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Fixed Income Securities [Member] | Corporate/Other debt securities | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 645.9 692.6  
Pension Plan | Fixed Income Securities [Member] | Corporate/Other debt securities | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Commingled Funds | International Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 111.7 176.8  
Pension Plan | Commingled Funds | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Commingled Funds | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Commingled Funds | International Equities | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Commingled Funds | International Equities | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Commingled Funds | Fixed Income      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 349.1 337.6  
Pension Plan | Commingled Funds | Fixed Income | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Commingled Funds | Fixed Income | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Commingled Funds | Fixed Income | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Commingled Funds | Fixed Income | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Commingled Funds | United States Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 195.9 279.7  
Pension Plan | Commingled Funds | United States Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Commingled Funds | United States Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Commingled Funds | United States Equities | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Commingled Funds | United States Equities | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Commingled Funds | Short-Term Money Markets      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 55.0 78.8  
Pension Plan | Commingled Funds | Short-Term Money Markets | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Commingled Funds | Short-Term Money Markets | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Commingled Funds | Short-Term Money Markets | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Commingled Funds | Short-Term Money Markets | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 10.9 10.9  
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 4.5 6.6  
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.1 0.3  
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Real Estate [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 37.2 52.9  
Pension Plan | Real Estate [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Real Estate [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Pension Plan | Real Estate [Member] | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Real Estate [Member] | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Mutual Funds [Member] | International Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 38.7 55.4  
Pension Plan | Mutual Funds [Member] | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   55.4  
Pension Plan | Mutual Funds [Member] | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 38.7    
Pension Plan | Mutual Funds [Member] | International Equities | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Mutual Funds [Member] | International Equities | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Mutual Funds [Member] | U.S. Multi-Strategy [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 128.4 161.3  
Pension Plan | Mutual Funds [Member] | U.S. Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   161.3  
Pension Plan | Mutual Funds [Member] | U.S. Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 128.4    
Pension Plan | Mutual Funds [Member] | U.S. Multi-Strategy [Member] | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Mutual Funds [Member] | U.S. Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Pension Plan | Mutual Funds [Member] | Fixed Income      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.1  
Pension Plan | Mutual Funds [Member] | Fixed Income | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.1  
Pension Plan | Mutual Funds [Member] | Fixed Income | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Pension Plan | Mutual Funds [Member] | Fixed Income | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Other Postretirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items 293.4 286.4  
Other Postretirement Benefits | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items   240.7  
Other Postretirement Benefits | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items 246.7    
Other Postretirement Benefits | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items 0.0 0.0  
Other Postretirement Benefits | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items 0.0 0.0  
Other Postretirement Benefits | Fair Value, Inputs, Level 1, 2 and 3      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 293.7 286.4 $ 261.4
Other Postretirement Benefits | International Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 50.5 48.2  
Other Postretirement Benefits | Fixed Income      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 118.8 122.0  
Other Postretirement Benefits | Due To Brokers Net [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount (1.8) (1.6)  
Other Postretirement Benefits | Due To Brokers Net [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Other Postretirement Benefits | Due To Brokers Net [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Other Postretirement Benefits | Due To Brokers Net [Member] | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount (1.8) (1.6)  
Other Postretirement Benefits | Due To Brokers Net [Member] | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Accrued Investment Income Dividends [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 8.0 8.6  
Other Postretirement Benefits | Accrued Investment Income Dividends [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   8.6  
Other Postretirement Benefits | Accrued Investment Income Dividends [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 8.0    
Other Postretirement Benefits | Accrued Investment Income Dividends [Member] | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Accrued Investment Income Dividends [Member] | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Receivables/Payables      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.3    
Other Postretirement Benefits | Receivables/Payables | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Other Postretirement Benefits | Receivables/Payables | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.3    
Other Postretirement Benefits | Receivables/Payables | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Other Postretirement Benefits | Commingled Funds | International Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 26.1 24.1  
Other Postretirement Benefits | Commingled Funds | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Other Postretirement Benefits | Commingled Funds | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Other Postretirement Benefits | Commingled Funds | International Equities | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Commingled Funds | International Equities | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Commingled Funds | United States Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 14.8 14.0  
Other Postretirement Benefits | Commingled Funds | United States Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Other Postretirement Benefits | Commingled Funds | United States Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Other Postretirement Benefits | Commingled Funds | United States Equities | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Commingled Funds | United States Equities | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Commingled Funds | Short-Term Money Markets      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 5.8 7.6  
Other Postretirement Benefits | Commingled Funds | Short-Term Money Markets | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   0.0  
Other Postretirement Benefits | Commingled Funds | Short-Term Money Markets | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0    
Other Postretirement Benefits | Commingled Funds | Short-Term Money Markets | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Commingled Funds | Short-Term Money Markets | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Mutual Funds [Member] | International Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 24.4 24.1  
Other Postretirement Benefits | Mutual Funds [Member] | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   24.1  
Other Postretirement Benefits | Mutual Funds [Member] | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 24.4    
Other Postretirement Benefits | Mutual Funds [Member] | International Equities | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Mutual Funds [Member] | International Equities | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 118.5 121.8  
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   121.8  
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 118.5    
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Mutual Funds [Member] | United States Equities      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 103.8 94.8  
Other Postretirement Benefits | Mutual Funds [Member] | United States Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount   94.8  
Other Postretirement Benefits | Mutual Funds [Member] | United States Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Fair Value, Recurring      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 103.8    
Other Postretirement Benefits | Mutual Funds [Member] | United States Equities | Significant Other Observable Inputs (Level 2) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Other Postretirement Benefits | Mutual Funds [Member] | United States Equities | Significant Unobservable Inputs (Level 3) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Underfunded Plan [Member] | Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 1,981.7 2,117.7  
Underfunded Plan [Member] | Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount $ 0.0 $ 0.0