Investments Net Investment Income (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 1,415.9	$ 1,394.9	$ 1,465.9
Less: investment expense	48.9	46.1	45.0
Net investment income	1,367.0	1,348.8	1,420.9
Fixed maturities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	1,199.4	1,222.5	1,224.2
Investments in fixed maturities not producing income		0
Equity securities, available-for-sale
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	2.8	7.5	13.6
Mortgage loans on real estate
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	157.1	143.5	118.1
Policy loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	13.1	13.2	13.7
Short-term investments and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	0.9	1.4	0.8
Other
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 42.6	$ 6.8	$ 95.5