Income From Investments - Net Investment Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investment Income:
Short-term Investments									$ 0.2	$ 0.1	$ 0.3
Loans to Policyholders									18.9	17.7	16.5
Real Estate									27.4	26.0	27.1
Equity Method Limited Liability Investments									9.3	9.6	48.8
Other									0.1	0.3	0
Total Investment Income									327.7	325.5	352.5
Investment Expenses:
Other Investment Expenses									31.8	27.5	26.8
Net Investment Income	72.9	70.4	75.2	77.4	75.3	58.6	82.9	81.2	295.9	298.0	325.7
Accrued Investment Income Receivable	72.4				76.1				72.4	76.1
Real Estate Investment [Member]
Investment Expenses:
Other Investment Expenses									26.1	25.9	25.7
Other Investment [Member]
Investment Expenses:
Other Investment Expenses									5.7	1.6	1.1
Fixed Maturities [Member]
Investment Income:
Interest and Dividends on Fixed Maturities									246.1	246.6	243.8
Equity Securities [Member]
Investment Income:
Dividends on Equity Securities									$ 25.7	$ 25.2	$ 16.0