Debt and Credit Arrangements Debt Transactions (Details) - 4.75% Notes Due 2030 (less unamortized discount and issuance costs of $3.8 and $6.2, respectively) $ in Millions	Mar. 31, 2020 USD ($)
Debt Instrument [Line Items]
Par Value	$ 650.0
Debt Instrument, Interest Rate, Stated Percentage	4.75%
Unsecured Debt	$ 640.0
Debt Instrument, Unamortized Discount	3.8
Unamortized Debt Issuance Expense	$ 6.2

Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt discount.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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