Fair Value (Carrying And Estimated Fair Values by Level Of Financial Instruments Not Recorded At Fair Value On Consolidated Balance Sheet) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other invested assets, long-term	$ 1,593.8	$ 1,542.6
Short-term borrowings	590.0	400.0
Convertible debentures	968.1
Carrying Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other invested assets, long-term	1,593.8	1,542.6
Short-term borrowings	590.0	400.0
Commercial paper	758.6	379.2
Notes	12,724.1	12,746.4
Convertible debentures	968.1	966.0
Level I [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other invested assets, long-term	0	0
Short-term borrowings	0	0
Commercial paper	0	0
Notes	0	0
Convertible debentures	0	0
Level II [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other invested assets, long-term	0	0
Short-term borrowings	590.0	400.0
Commercial paper	758.6	379.2
Notes	13,285.1	13,014.3
Convertible debentures	2,192.8	2,030.6
Level III [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other invested assets, long-term	1,593.8	1,542.6
Short-term borrowings	0	0
Commercial paper	0	0
Notes	0	0
Convertible debentures	0	0
Total [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other invested assets, long-term	1,593.8	1,542.6
Short-term borrowings	590.0	400.0
Commercial paper	758.6	379.2
Notes	13,285.1	13,014.3
Convertible debentures	$ 2,192.8	$ 2,030.6