Debt and Credit Facilities (Short-Term Borrowings and Current Maturities of Long-Term Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Short-term borrowings and current maturities of long-term debt	$ 775.1	$ 650.3
Debentures With Put Feature [Member]
Short-term borrowings and current maturities of long-term debt	343.0	343.0
Two Point Six Two Five Percent Senior Notes Due Two Thousand Twenty [Member]
Short-term borrowings and current maturities of long-term debt	$ 0.0	$ 299.8
Debt Instrument, Interest Rate, Stated Percentage	2.625%	2.625%
Two Point Nine Percent Senior Notes Due Two Thousand Twenty One [Member] [Member]
Short-term borrowings and current maturities of long-term debt	$ 299.6	$ 0.0
Debt Instrument, Interest Rate, Stated Percentage	2.90%
Commercial Paper [Member]
Short-term borrowings and current maturities of long-term debt		0.0	$ 0.0
Current Maturities Of Long Term Debt [Member]
Short-term borrowings and current maturities of long-term debt	$ 7.5	7.5
9.00% Debentures Due 2021 [Member]
Short-term borrowings and current maturities of long-term debt	$ 125.0	$ 0.0
Debt Instrument, Interest Rate, Stated Percentage	9.00%
Two Point Nine Percent Senior Notes Due Two Thousand Twenty One [Member] [Member]
Debt Instrument, Interest Rate, Stated Percentage		2.90%