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Fair Value Measurements (Schedule Of Carrying Values And Estimated Fair Values Of Debt Instruments) (Details) - USD ($) $ in Millions | Sep. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Amounts borrowed under the credit facility | $ 140.6 |  | $ 0.0
Less: current maturities | 125.5 |  | 0.0
Total long-term debt, carrying value | 6,042.3 |  | 5,010.4
Total outstanding borrowings under credit facility | 140.6 |  |
Unamortized deferred financing cost | 7.7 |  |
Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | 6,167.8 |  | 5,010.4
Less: current maturities | 125.5 |  | 0.0
Total long-term debt, carrying value | 6,042.3 |  | 5,010.4
Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | 3,958.1 |  | 3,545.8
Less: current maturities | 121.3 |  | 0.0
Total long-term debt, estimated fair value | 3,836.8 |  | 3,545.8
Line of Credit | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | 132.9 |  | 0.0
Line of Credit | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Amounts borrowed under the credit facility | $ 140.6 |  | 0.0
7.88% Senior notes due 2019 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 6.875% | 6.875% |
7.88% Senior notes due 2019 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 125.5 |  | 127.5
7.88% Senior notes due 2019 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 121.3 |  | 121.6
4.70% Senior notes due 2021 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 4.70% | 4.70% |
4.70% Senior notes due 2021 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 113.1 |  | 112.7
4.70% Senior notes due 2021 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 98.7 |  | 101.8
4.875% Senior Notes Due 2022 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 4.875% | 4.875% |
4.875% Senior Notes Due 2022 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 597.1 |  | 0.0
4.875% Senior Notes Due 2022 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 474.9 |  | 0.0
3.00% exchangeable senior notes due 2024 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 3.00% | 3.00% |
3.00% exchangeable senior notes due 2024 | Convertible Debt |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying value of 2024 convertible notes | $ 838.0 |  | 836.3
3.00% exchangeable senior notes due 2024 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | 691.0 |  | 666.8
3.00% exchangeable senior notes due 2024 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 573.4 |  | 575.5
4.50% Senior Notes due 2024 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 4.50% | 4.50% |
4.50% Senior Notes due 2024 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 301.9 |  | 619.8
4.50% Senior Notes due 2024 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 170.5 |  | 405.2
4.75% Senior notes due 2024 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 4.75% | 4.75% |
4.75% Senior notes due 2024 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 274.3 |  | 0.0
4.75% Senior notes due 2024 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 197.9 |  | 0.0
8.00% Senior notes due 2024 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 8.00% | 8.00% |
8.00% Senior notes due 2024 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 296.0 |  | 337.0
8.00% Senior notes due 2024 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 195.4 |  | 273.7
7.375% Senior notes due 2025 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 7.375% | 7.375% |
7.375% Senior notes due 2025 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 328.1 |  | 0.0
7.375% Senior notes due 2025 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 214.1 |  | 0.0
5.20% Senior notes due 2025 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 5.20% | 5.20% |
5.20% Senior notes due 2025 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 331.6 |  | 664.4
5.20% Senior notes due 2025 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 180.3 |  | 443.9
7.75% Senior notes due 2026 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 7.75% | 7.75% |
7.75% Senior notes due 2026 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 986.6 |  | 985.0
7.75% Senior notes due 2026 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 541.9 |  | 725.5
7.20% Senior notes due 2027 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 7.20% | 7.20% |
7.20% Senior notes due 2027 | Debentures | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 111.6 |  | 149.3
7.20% Senior notes due 2027 | Debentures | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 70.5 |  | 109.1
7.875% Senior notes due 2040 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 7.875% | 7.875% |
7.875% Senior notes due 2040 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 373.7 |  | 375.0
7.875% Senior notes due 2040 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 155.3 |  | 223.2
5.40% Senior Notes Due 2042 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 5.40% | 5.40% |
5.40% Senior Notes Due 2042 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 262.3 |  | 0.0
5.40% Senior Notes Due 2042 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 192.2 |  | 0.0
5.75% Senior notes due 2044 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 5.75% | 5.75% |
5.75% Senior notes due 2044 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 973.7 |  | 972.9
5.75% Senior notes due 2044 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 434.0 |  | 566.3
5.85% Senior Notes Due 2044 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Debt instrument interest rate stated percentage | 5.85% | 5.85% |
5.85% Senior Notes Due 2044 | Senior Notes | Carrying Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Carrying Value | $ 268.4 |  | 0.0
5.85% Senior Notes Due 2044 | Senior Notes | Estimate of Fair Value |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Estimated Fair Value | $ 197.1 |  | $ 0.0

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 + Details
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- Definition Fair value of the amount outstanding under the credit facility. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611 + Details
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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. + References No definition available. + Details
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- Definition Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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