Investments (Aggregate Fair Value And Gross Unrealized Loss Of Fixed Maturity Securities And Equity Securities In An Unrealized Loss Position) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014 securities	Dec. 31, 2013 securities
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	2,675	3,451
Estimated Fair Value, Less Than 12 Months	$ 4,409.3	$ 6,636.9
Gross Unrealized Loss, Less Than 12 Months	(74.8)	(244.5)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	777	250
Estimated Fair Value, 12 Months or Greater	1,548.4	301.7
Gross Unrealized Losses, 12 Months or Greater	(59.8)	(33.3)
Equity Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	510	426
Estimated Fair Value, Less Than 12 Months	161.5	120.8
Gross Unrealized Loss, Less Than 12 Months	(13.7)	(8.0)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	0	0
Estimated Fair Value, 12 Months or Greater	0	0
Gross Unrealized Losses, 12 Months or Greater	0	0
Fixed Maturities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	2,165	3,025
Estimated Fair Value, Less Than 12 Months	4,247.8	6,516.1
Gross Unrealized Loss, Less Than 12 Months	(61.1)	(236.5)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	777	250
Estimated Fair Value, 12 Months or Greater	1,548.4	301.7
Gross Unrealized Losses, 12 Months or Greater	(59.8)	(33.3)
Fixed Maturities [Member] | United States Government Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	12	27
Estimated Fair Value, Less Than 12 Months	53.6	179.2
Gross Unrealized Loss, Less Than 12 Months	(0.1)	(3.4)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	3	0
Estimated Fair Value, 12 Months or Greater	5.0	0
Gross Unrealized Losses, 12 Months or Greater	(0.2)	0
Fixed Maturities [Member] | Government Sponsored Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	10	22
Estimated Fair Value, Less Than 12 Months	27.0	73.4
Gross Unrealized Loss, Less Than 12 Months	(0.1)	(1.3)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	16	0
Estimated Fair Value, 12 Months or Greater	31.8	0
Gross Unrealized Losses, 12 Months or Greater	(0.7)	0
Fixed Maturities [Member] | States, Municipalities And Political Subdivisions, Tax-Exempt [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	95	806
Estimated Fair Value, Less Than 12 Months	253.6	2,070.9
Gross Unrealized Loss, Less Than 12 Months	(1.5)	(90.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	126	42
Estimated Fair Value, 12 Months or Greater	320.4	82.4
Gross Unrealized Losses, 12 Months or Greater	(6.1)	(9.6)
Fixed Maturities [Member] | Corporate Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	1,828	1,448
Estimated Fair Value, Less Than 12 Months	3,281.2	2,586.6
Gross Unrealized Loss, Less Than 12 Months	(56.2)	(95.2)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	336	107
Estimated Fair Value, 12 Months or Greater	579.7	81.3
Gross Unrealized Losses, 12 Months or Greater	(34.5)	(15.5)
Fixed Maturities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	132	605
Estimated Fair Value, Less Than 12 Months	318.7	1,243.0
Gross Unrealized Loss, Less Than 12 Months	(2.0)	(41.4)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	251	80
Estimated Fair Value, 12 Months or Greater	483.9	116.2
Gross Unrealized Losses, 12 Months or Greater	(16.4)	(7.1)
Fixed Maturities [Member] | Commercial Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	37	52
Estimated Fair Value, Less Than 12 Months	123.9	177.7
Gross Unrealized Loss, Less Than 12 Months	(0.5)	(2.6)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	17	4
Estimated Fair Value, 12 Months or Greater	53.5	5.6
Gross Unrealized Losses, 12 Months or Greater	(0.7)	(0.3)
Fixed Maturities [Member] | Other Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	51	65
Estimated Fair Value, Less Than 12 Months	189.8	185.3
Gross Unrealized Loss, Less Than 12 Months	(0.7)	(2.5)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	28	17
Estimated Fair Value, 12 Months or Greater	74.1	16.2
Gross Unrealized Losses, 12 Months or Greater	$ (1.2)	$ (0.8)