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BENEFIT PLANS - Schedule of Assets by Fair Value (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 3,666.2 $ 4,118.2 $ 4,124.7
Year End Allocation 100.00% 100.00%  
OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 1,775.9 $ 1,673.3 $ 1,549.3
Year End Allocation 100.00% 100.00%  
Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 791.0 $ 809.4  
Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,033.1 897.8  
Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,788.9 2,252.1  
Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 463.5 501.2  
Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.1  
Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,086.3 1,056.6  
Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 279.3 274.3  
Equities | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 1,265.9 $ 1,222.0  
Year End Allocation 34.50% 29.70%  
Equities | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 1,077.6 $ 960.6  
Year End Allocation 60.60% 57.40%  
Equities | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 793.3 $ 801.1  
Equities | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 948.2 829.0  
Equities | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Equities | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Equities | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Equities | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Equities | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 472.6 420.9  
Equities | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 129.4 131.6  
Domestic | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 327.0 $ 411.3  
Year End Allocation 8.90% 10.00%  
Domestic | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 616.8 $ 540.6  
Year End Allocation 34.70% 32.30%  
Domestic | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 327.0 $ 411.3  
Domestic | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 616.8 540.6  
Domestic | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Domestic | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Domestic | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Domestic | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Domestic | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Domestic | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
International | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 290.2 $ 389.8  
Year End Allocation 7.90% 9.50%  
International | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 267.2 $ 288.4  
Year End Allocation 15.00% 17.20%  
International | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 290.2 $ 389.8  
International | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 267.2 288.4  
International | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
International | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
International | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
International | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
International | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
International | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Common Collective Trusts | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 648.7 $ 420.9  
Year End Allocation 17.70% 10.20%  
Common Collective Trusts | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 193.6 $ 131.6  
Year End Allocation 10.90% 7.90%  
Common Collective Trusts | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 176.1 $ 0.0  
Common Collective Trusts | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 64.2 0.0  
Common Collective Trusts | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Common Collective Trusts | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Common Collective Trusts | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Common Collective Trusts | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Common Collective Trusts | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 472.6 420.9  
Common Collective Trusts | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 129.4 131.6  
Fixed Income | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 1,745.3 $ 2,209.4  
Year End Allocation 47.60% 53.60%  
Fixed Income | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 512.4 $ 538.5  
Year End Allocation 28.90% 32.20%  
Fixed Income | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ (2.3) $ 8.3  
Fixed Income | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 57.3 42.9  
Fixed Income | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,747.6 2,201.1  
Fixed Income | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 322.2 348.9  
Fixed Income | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Fixed Income | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Fixed Income | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Fixed Income | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 132.9 146.7  
Common Collective Trust - Debt | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 132.9 $ 146.7  
Year End Allocation 7.50% 8.80%  
Common Collective Trust - Debt | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
Common Collective Trust - Debt | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Common Collective Trust - Debt | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Common Collective Trust - Debt | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 132.9 146.7  
United States Government and Agency Securities | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 863.3 $ 1,107.5  
Year End Allocation 23.60% 26.90%  
United States Government and Agency Securities | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 157.1 $ 164.7  
Year End Allocation 8.90% 9.80%  
United States Government and Agency Securities | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ (2.3) $ 8.3  
United States Government and Agency Securities | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets (0.5) 1.4  
United States Government and Agency Securities | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 865.6 1,099.2  
United States Government and Agency Securities | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 157.6 163.3  
United States Government and Agency Securities | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States Government and Agency Securities | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States Government and Agency Securities | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States Government and Agency Securities | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Corporate Debt | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 719.2 $ 894.8  
Year End Allocation 19.60% 21.70%  
Corporate Debt | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 132.3 $ 149.0  
Year End Allocation 7.50% 8.90%  
Corporate Debt | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
Corporate Debt | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Corporate Debt | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 719.2 894.8  
Corporate Debt | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 132.3 149.0  
Corporate Debt | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Corporate Debt | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Corporate Debt | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Corporate Debt | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Foreign Debt | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 136.1 $ 167.1  
Year End Allocation 3.70% 4.10%  
Foreign Debt | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 27.1 $ 28.6  
Year End Allocation 1.50% 1.70%  
Foreign Debt | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
Foreign Debt | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Foreign Debt | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 136.1 167.1  
Foreign Debt | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 27.1 28.6  
Foreign Debt | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Foreign Debt | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Foreign Debt | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Foreign Debt | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
State and Local Government | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 25.8 $ 38.7  
Year End Allocation 0.70% 0.90%  
State and Local Government | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 62.8 $ 49.3  
Year End Allocation 3.50% 3.00%  
State and Local Government | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
State and Local Government | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 57.8 41.5  
State and Local Government | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 25.8 38.7  
State and Local Government | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 5.0 7.8  
State and Local Government | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
State and Local Government | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
State and Local Government | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
State and Local Government | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Other – Asset Backed | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.9 $ 1.3  
Year End Allocation 0.00% 0.00%  
Other – Asset Backed | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.2 $ 0.2  
Year End Allocation 0.00% 0.00%  
Other – Asset Backed | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
Other – Asset Backed | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Other – Asset Backed | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.9 1.3  
Other – Asset Backed | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.2 0.2  
Other – Asset Backed | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Other – Asset Backed | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Other – Asset Backed | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Other – Asset Backed | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Infrastructure | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 112.9 $ 101.4  
Year End Allocation 3.10% 2.50%  
Infrastructure | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
Infrastructure | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Infrastructure | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Infrastructure | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 112.9 101.4  
Real Estate | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 227.9 $ 239.3  
Year End Allocation 6.20% 5.80%  
Real Estate | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
Real Estate | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Real Estate | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Real Estate | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 227.9 239.3  
Alternative Investments | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 223.8 $ 241.8  
Year End Allocation 6.10% 5.80%  
Alternative Investments | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
Alternative Investments | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Alternative Investments | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Alternative Investments | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 223.8 241.8  
Trusted Owned Life Insurance | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 141.3 $ 152.3  
Year End Allocation 8.00% 9.10%  
Trusted Owned Life Insurance | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
Trusted Owned Life Insurance | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 141.3 152.3  
Trusted Owned Life Insurance | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Trusted Owned Life Insurance | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
International Equities | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 23.1 $ 22.3  
Year End Allocation 1.30% 1.30%  
International Equities | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
International Equities | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 23.1 22.3  
International Equities | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
International Equities | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States Bonds | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 118.2 $ 130.0  
Year End Allocation 6.70% 7.80%  
United States Bonds | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
United States Bonds | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 118.2 130.0  
United States Bonds | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States Bonds | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Cash and Cash Equivalents | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 68.5 $ 84.8  
Year End Allocation 1.90% 2.10%  
Cash and Cash Equivalents | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 30.7 $ 28.8  
Year End Allocation 1.70% 1.70%  
Cash and Cash Equivalents | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
Cash and Cash Equivalents | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 27.6 25.9  
Cash and Cash Equivalents | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 41.3 51.0  
Cash and Cash Equivalents | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Cash and Cash Equivalents | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Cash and Cash Equivalents | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Cash and Cash Equivalents | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 27.2 33.8  
Cash and Cash Equivalents | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 3.1 2.9  
Other Pending Transactions and Accrued Income | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 21.9 $ 19.5  
Year End Allocation 0.60% 0.50%  
Other Pending Transactions and Accrued Income | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 13.9 $ (6.9)  
Year End Allocation 0.80% (0.40%)  
Other Pending Transactions and Accrued Income | Level 1 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0  
Other Pending Transactions and Accrued Income | Level 1 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Other Pending Transactions and Accrued Income | Level 2 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Other Pending Transactions and Accrued Income | Level 2 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Other Pending Transactions and Accrued Income | Level 3 | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.1  
Other Pending Transactions and Accrued Income | Level 3 | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Other Pending Transactions and Accrued Income | Other | Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 21.9 19.4  
Other Pending Transactions and Accrued Income | Other | OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 13.9 $ (6.9)