Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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(Aggregate Maturities Of Long-Term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Mar. 04, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Feb. 28, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2011
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	$ (951.8)		$ (721.8)	$ (595.4)
Long-Term Debt, Gross	6,515.3							$ 6,049.5
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount								(311.2)	$ (1,093.1)
Debt Instrument, Repurchased Face Amount Net of Debt Issuance	(12.8)		1,367.1		$ 515.8
Senior Notes [Member] \| 6.875% Senior notes due 2020
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount				$ (71.4)	(229.9)		$ (328.0)	(219.2)
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	122.9
Face (Par) Amount of the Original Debt Instrument, Including Repurchases and Equity Exchanges								900.0
Debt Instrument, Face Amount												$ 900.0
Senior Notes [Member] \| 4.70% Senior notes due 2021
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount		$ (12.8)	(156.2)		(413.3)	$ (156.2)		(817.0)
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	100.7
Face (Par) Amount of the Original Debt Instrument, Including Repurchases and Equity Exchanges								1,500.0
Debt Instrument, Face Amount													$ 1,500.0
Senior Notes [Member] \| 4.875%SeniorNotesDue2022Member [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Year Two	620.8
Debt Instrument, Face Amount	620.8
Senior Notes [Member] \| 4.50% Senior notes due 2024
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	(320.0)							(1.6)
Long-term Debt, Maturities, Repayments of Principal in Year Four	303.4
Face (Par) Amount of the Original Debt Instrument, Including Repurchases and Equity Exchanges								625.0
Debt Instrument, Face Amount											$ 625.0
Senior Notes [Member] \| 4.75%SeniorNotesDue2024Member [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	(79.5)
Long-term Debt, Maturities, Repayments of Principal in Year Four	318.6
Long-Term Debt, Maturities, Repayments of Principal after Year Five	318.6
Debt Instrument, Face Amount	398.1
Senior Notes [Member] \| 8.00% Senior notes due 2024
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	(39.7)
Long-term Debt, Maturities, Repayments of Principal in Year Four	292.3
Face (Par) Amount of the Original Debt Instrument, Including Repurchases and Equity Exchanges					332.0
Debt Instrument, Face Amount								332.0
Senior Notes [Member] \| 5.20% Senior notes due 2025
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	(335.5)							(30.8)
Long-term Debt, Maturities, Repayments of Principal in Year Five	333.7
Face (Par) Amount of the Original Debt Instrument, Including Repurchases and Equity Exchanges								700.0
Debt Instrument, Face Amount										$ 700.0
Senior Notes [Member] \| 7.38%SeniorNotesDue2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	(139.2)
Long-term Debt, Maturities, Repayments of Principal in Year Five	360.8
Long-Term Debt, Maturities, Repayments of Principal after Year Five	360.8
Debt Instrument, Face Amount	500.0
Senior Notes [Member] \| 7.75% Senior notes due 2026
Debt Instrument [Line Items]
Long-Term Debt, Maturities, Repayments of Principal after Year Five	1,000.0
Debt Instrument, Face Amount			1,000.0		$ 1,000.0
Senior Notes [Member] \| 7.20% Senior notes due 2027
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	(37.9)
Long-Term Debt, Maturities, Repayments of Principal after Year Five	112.1
Face (Par) Amount of the Original Debt Instrument, Including Repurchases and Equity Exchanges								150.0
Debt Instrument, Face Amount			150.0
Senior Notes [Member] \| 7.875% Senior notes due 2040
Debt Instrument [Line Items]
Long-Term Debt, Maturities, Repayments of Principal after Year Five	300.0
Debt Instrument, Face Amount								300.0				$ 300.0
Senior Notes [Member] \| 5.40%SeniorNotesDue2042 [Member]
Debt Instrument [Line Items]
Long-Term Debt, Maturities, Repayments of Principal after Year Five	400.0
Debt Instrument, Face Amount	400.0
Senior Notes [Member] \| 5.75% Senior notes due 2044
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount								(24.5)
Long-Term Debt, Maturities, Repayments of Principal after Year Five	1,000.5
Face (Par) Amount of the Original Debt Instrument, Including Repurchases and Equity Exchanges								1,025.0
Debt Instrument, Face Amount										$ 400.0	$ 625.0
Senior Notes [Member] \| 5.85%SeniorNotesDue2044 [Member]
Debt Instrument [Line Items]
Long-Term Debt, Maturities, Repayments of Principal after Year Five	400.0
Debt Instrument, Face Amount	400.0
Convertible Debt [Member] \| 3.00% Exchangeable senior notes due 2024
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Year Four	849.5
Debt Instrument, Face Amount	$ 849.5		$ 849.5					$ 849.5