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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(Aggregate Maturities Of Long-Term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Mar. 31, 2018	Feb. 28, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2012
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	$ (951.8)		$ (721.8)	$ (595.4)		$ (194.1)
Long-Term Debt, Gross	6,528.1								$ 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	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)	$ (328.0)	(229.9)	$ (100.1)		(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			(156.2)	$ (156.2)		(413.3)	$ (39.4)		(817.0)
Long-term Debt, Maturities, Repayments of Principal in Year Two	113.5
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 Three	620.8
Debt Instrument, Face Amount	620.8
Senior Notes [Member] \| 4.50% Senior notes due 2024(1)
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	(320.0)								(1.7)
Long-term Debt, Maturities, Repayments of Principal in Year Five	303.3
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 after Year Five	318.6
Debt Instrument, Face Amount	398.1
Senior Notes [Member] \| 8.00% Senior notes due 2024(1)
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	(39.7)
Long-Term Debt, Maturities, Repayments of Principal after Year Five	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(1)
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	(335.5)								(30.7)
Long-Term Debt, Maturities, Repayments of Principal after Year Five	333.8
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 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(2)
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