Investments (Net Realized Investment Gains/Losses And Net Change In Unrealized Appreciation/Depreciation In Investments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investment [Line Items]
Gross realized gains from sales	$ 498.1	$ 483.5	$ 368.2
Gross realized losses from sales	(226.2)	(148.6)	(133.1)
Other realized gains (losses) on investments	48.1	0.5	3.6
Net realized gains on investments	271.9	334.9	235.1
Other-than-temporary impairment losses recognized in income	(98.9)	(37.8)	(93.3)
Total change in net unrealized gains (losses) on investments	(454.4)	294.5	31.3
Deferred income tax benefit (expense)	159.7	(104.6)	(10.7)
Net change in net unrealized gains (losses) on investments	(294.7)	189.9	20.6
Net realized gains (losses) on investments, other-than-temporary impairment losses recognized in income and net change in net unrealized gains (losses) on investments	(121.7)	487.0	162.4
Fixed Maturity Securities [Member]
Investment [Line Items]
Gross realized gains from sales	225.9	401.0	289.2
Gross realized losses from sales	(125.7)	(54.8)	(65.1)
Net realized gains (losses) from sales	100.2	346.2	224.1
Other-than-temporary impairment losses recognized in income	(42.5)	(11.8)	(24.2)
Total change in net unrealized gains (losses) on investments	(679.8)	199.8	155.9
Equity Securities [Member]
Investment [Line Items]
Gross realized gains from sales	224.1	82.0	75.4
Gross realized losses from sales	(100.5)	(93.8)	(68.0)
Net realized gains (losses) from sales	123.6	(11.8)	7.4
Other-than-temporary impairment losses recognized in income	(13.9)	(17.5)	(27.9)
Total change in net unrealized gains (losses) on investments	225.4	94.7	(124.6)
Other Long-term Investments [Member]
Investment [Line Items]
Other-than-temporary impairment losses recognized in income	$ (42.5)	$ (8.5)	$ (41.2)