Fair Value Measurements (Schedule Of Carrying Values And Estimated Fair Values Of Debt Instruments) (Details) - USD ($) $ in Millions | Mar. 31, 2020 | Dec. 31, 2019 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt, Current Maturities | $ 224.5 | $ 124.8 |
Short-term Debt, Fair Value | 0 | 0 |
LONG-TERM DEBT | 6,148.6 | $ 5,923.5 |
Long-term Line of Credit | 328.9 | |
Unamortized Debt Issuance Expense | 6 | |
Letters of credit outstanding, amount | 117.9 | |
Revolving Credit Facility [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Letters of credit outstanding, amount | 3.2 | |
Line of Credit Facility, Maximum Borrowing Capacity | $ 1,300 | |
7.88% Senior Notes Due 2019 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 7.88% | 7.88% |
Six Point Eight Seven Five Percent Senior Notes Due Two Thousand Twenty Member | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 6.875% | 6.875% |
Four Point Seven Zero Percent Senior Notes Member | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 4.70% | 4.70% |
4.875% Senior Notes Due 2022 Member [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 4.58% | 4.58% |
4.875% Senior Notes Due 2022 Member [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 4.875% | |
Three percent exchangeable senior notes due twenty twenty four [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 3.00% | 3.00% |
Three percent exchangeable senior notes due twenty twenty four [Member] | Convertible Debt [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
3.00% exchangeable senior notes, excluding discount and net of debt issuance costs | $ 839.2 | $ 838.3 |
Four Point Five Percent Senior Notes Member [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 4.50% | 4.50% |
4.75% Senior Notes Due 2024 [Member] | | |
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 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 4.75% | |
8.00% senior notes due 2024 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 8.00% | 8.00% |
7.38% Senior Notes Due 2025 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 7.38% | 7.38% |
7.38% Senior Notes Due 2025 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 7.375% | |
Five Point Two Percent Senior Notes [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 5.20% | 5.20% |
Seven Point Seven Five Percent Senior Notes Due Two Thousand Twenty Six [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 7.75% | 7.75% |
Seven Point Two Zero Percent Debentures Member | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 7.20% | 7.20% |
Seven Point Eight Seven Five Percent Senior Notes Member | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 7.875% | 7.875% |
Seven Point Eight Seven Five Percent Senior Notes Member | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 7.875% | |
5.40% Senior Notes Due 2042 [Member] | | |
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 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 5.40% | |
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% |
5.85% Senior Notes Due 2044 [Member] | | |
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 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Debt instrument interest rate stated percentage | 5.85% | |
Reported Value Measurement [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | $ 6,373.1 | $ 6,048.3 |
LONG-TERM DEBT | 6,148.6 | 5,923.5 |
Reported Value Measurement [Member] | Line of Credit [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 322.9 | 0 |
Reported Value Measurement [Member] | Six Point Eight Seven Five Percent Senior Notes Due Two Thousand Twenty Member | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 124.1 | 124.8 |
Reported Value Measurement [Member] | Four Point Seven Zero Percent Senior Notes Member | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 100.4 | 113.2 |
Reported Value Measurement [Member] | 4.875% Senior Notes Due 2022 Member [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 601.2 | 599.2 |
Reported Value Measurement [Member] | Three percent exchangeable senior notes due twenty twenty four [Member] | Convertible Debt [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 707.7 | 699 |
Reported Value Measurement [Member] | Four Point Five Percent Senior Notes Member [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 302 | 302 |
Reported Value Measurement [Member] | 4.75% Senior Notes Due 2024 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 278.6 | 276.5 |
Reported Value Measurement [Member] | 8.00% senior notes due 2024 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 295.5 | 295.7 |
Reported Value Measurement [Member] | 7.38% Senior Notes Due 2025 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 330.2 | 329.2 |
Reported Value Measurement [Member] | Five Point Two Percent Senior Notes [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 331.8 | 331.7 |
Reported Value Measurement [Member] | Seven Point Seven Five Percent Senior Notes Due Two Thousand Twenty Six [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 987.7 | 987.1 |
Reported Value Measurement [Member] | Seven Point Two Zero Percent Debentures Member | Debentures Due2027 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 111.7 | 111.7 |
Reported Value Measurement [Member] | Seven Point Eight Seven Five Percent Senior Notes Member | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 372.8 | 373.3 |
Reported Value Measurement [Member] | 5.40% Senior Notes Due 2042 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 263.2 | 262.8 |
Reported Value Measurement [Member] | 5.75% Senior notes due 2044 | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 974.2 | 973.3 |
Reported Value Measurement [Member] | 5.85% Senior Notes Due 2044 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Long-term Debt | 269.1 | 268.8 |
Estimate of Fair Value Measurement [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 1,368.2 | 3,874.1 |
Long-term Debt, Fair Value | 1,368.2 | 3,874.1 |
Estimate of Fair Value Measurement [Member] | Line of Credit [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 328.9 | 0 |
Estimate of Fair Value Measurement [Member] | Six Point Eight Seven Five Percent Senior Notes Due Two Thousand Twenty Member | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 27.8 | 117.3 |
Estimate of Fair Value Measurement [Member] | Four Point Seven Zero Percent Senior Notes Member | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 10.4 | 95.5 |
Estimate of Fair Value Measurement [Member] | 4.875% Senior Notes Due 2022 Member [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 125.9 | 460.5 |
Estimate of Fair Value Measurement [Member] | Three percent exchangeable senior notes due twenty twenty four [Member] | Convertible Debt [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 214.3 | 607.4 |
Estimate of Fair Value Measurement [Member] | Four Point Five Percent Senior Notes Member [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 28.6 | 167.2 |
Estimate of Fair Value Measurement [Member] | 4.75% Senior Notes Due 2024 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 64.2 | 201.4 |
Estimate of Fair Value Measurement [Member] | 8.00% senior notes due 2024 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 27.6 | 181.7 |
Estimate of Fair Value Measurement [Member] | 7.38% Senior Notes Due 2025 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 82.6 | 218.6 |
Estimate of Fair Value Measurement [Member] | Five Point Two Percent Senior Notes [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 33.8 | 186.7 |
Estimate of Fair Value Measurement [Member] | Seven Point Seven Five Percent Senior Notes Due Two Thousand Twenty Six [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 107.7 | 575.1 |
Estimate of Fair Value Measurement [Member] | Seven Point Two Zero Percent Debentures Member | Debentures Due2027 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 16.6 | 70 |
Estimate of Fair Value Measurement [Member] | Seven Point Eight Seven Five Percent Senior Notes Member | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 46.9 | 153.5 |
Estimate of Fair Value Measurement [Member] | 5.40% Senior Notes Due 2042 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 78.8 | 194.4 |
Estimate of Fair Value Measurement [Member] | 5.75% Senior notes due 2044 | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | 93.5 | 450 |
Estimate of Fair Value Measurement [Member] | 5.85% Senior Notes Due 2044 [Member] | Senior Notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Estimated Fair Value | $ 80.6 | $ 194.8 |