Debt and Credit Facilities (Long-Term Debt Excluding Current Maturities) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Mar. 31, 2019
Long-term debt excluding current maturities	$ 4,494.2	$ 4,922.9
Two Point Nine Percent Senior Notes Due Two Thousand Twenty One [Member] [Member]
Debt Instrument, Interest Rate, Stated Percentage		2.90%
Long-term debt excluding current maturities	0.0	$ 299.1
9.00% Debentures Due 2021 [Member]
Debt Instrument, Interest Rate, Stated Percentage		9.00%
Long-term debt excluding current maturities	$ 0.0	$ 124.9
4.25% Senior notes due 2023 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.25%	4.25%
Long-term debt excluding current maturities	$ 698.3	$ 697.8
Seven Point Two Zero Percent Debentures [Domain]
Long-term debt excluding current maturities	$ 29.9	$ 37.3
Three Point Five Five Percent Senior Notes due 2024 [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.55%	3.55%
Long-term debt excluding current maturities	$ 497.1	$ 496.6
6.48% Debentures Due 2025 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.48%	6.48%
Long-term debt excluding current maturities	$ 149.7	$ 149.7
Three Point Five Percent Senior notes Due Two Thousand Twenty Six [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.50%	3.50%
Long-term debt excluding current maturities	$ 397.2	$ 396.8	$ 400.0
Three Point Seven Five Percent Senior Notes Due Two Thousand Twenty Eight [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.75%	3.75%
Long-term debt excluding current maturities	$ 545.5	$ 545.1
Three Point Eight Percent Senior Notes Due Two Thousand Twenty Nine [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.80%	3.80%
Long-term debt excluding current maturities	$ 744.1	$ 743.6	750.0
5.75% Senior notes due 2043 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.75%	5.75%
Long-term debt excluding current maturities	$ 494.7	$ 494.5
Four Point Six Five Percent Senior Notes due Twenty Forty Four [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.65%	4.65%
Long-term debt excluding current maturities	$ 296.0	$ 295.9
Seven Point Two Zero Percent Debentures due Two Thousand Fourteen to Two Thousand Twenty Five [Member] [Member]
Debt Instrument, Interest Rate, Stated Percentage	7.20%	7.20%
Four Point Three Percent Senior Notes Due Two Thousand Forty Eight [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.30%	4.30%
Long-term debt excluding current maturities	$ 296.1	$ 296.0
Four Point Five Percent Senior Notes Due Two Thousand Forty Nine [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.50%	4.50%
Long-term debt excluding current maturities	$ 345.6	$ 345.5	$ 350.0
Other Loans and Notes [Member]
Long-term debt excluding current maturities	$ 0.0	$ 0.1

Two Point Nine Percent Senior Notes Due Two Thousand Twenty One [Member] [Member]

9.00% Debentures Due 2021 [Member]

4.25% Senior notes due 2023 [Member]

Seven Point Two Zero Percent Debentures [Domain]

Three Point Five Five Percent Senior Notes due 2024 [Member]

6.48% Debentures Due 2025 [Member]

Three Point Five Percent Senior notes Due Two Thousand Twenty Six [Member]

Three Point Seven Five Percent Senior Notes Due Two Thousand Twenty Eight [Member]

Three Point Eight Percent Senior Notes Due Two Thousand Twenty Nine [Member]

5.75% Senior notes due 2043 [Member]

Four Point Six Five Percent Senior Notes due Twenty Forty Four [Member]

Seven Point Two Zero Percent Debentures due Two Thousand Fourteen to Two Thousand Twenty Five [Member] [Member]

Four Point Three Percent Senior Notes Due Two Thousand Forty Eight [Member]

Four Point Five Percent Senior Notes Due Two Thousand Forty Nine [Member]

Other Loans and Notes [Member]