Reinsurance (Summary Of Direct, Assumed And Ceded Premiums Written And Earned) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reinsurance Disclosures [Abstract]
Direct - Premium written	$ 65,939.1	$ 56,443.6	$ 56,190.3
Assumed - Premium written	174.3	197.0	179.9
Ceded - Premium written	(92.6)	(73.2)	(84.2)
Net premiums - written	66,020.8	56,567.4	56,286.0
Percentage - assumed to net premiums - written	0.30%	0.30%	0.30%
Direct - Premiums earned	66,038.9	56,373.6	55,875.8
Assumed - Premium earned	174.0	196.4	178.5
Ceded - Premium earned	(93.8)	(73.3)	(84.7)
Premiums	$ 66,119.1	$ 56,496.7	$ 55,969.6
Percentage - assumed to net premiums - earned	0.30%	0.30%	0.30%