Income From Investments - Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investment Income:
Equity Method Limited Liability Investments									$ 19.0	$ 9.0	$ 26.4
Fair Value Option Investments									0.2	(0.7)	0.0
Short-term Investments									0.4	0.6	0.1
Real Estate									11.9	12.1	20.8
Loans to Policyholders									21.1	20.5	19.8
Other									0.0	0.1	0.0
Total Investment Income									321.2	328.9	340.6
Investment Expenses:
Other Investment Expenses									18.6	19.8	25.9
Net Investment Income	$ 79.4	$ 75.9	$ 76.7	$ 70.6	$ 93.1	$ 72.3	$ 72.6	$ 71.1	302.6	309.1	314.7
Accrued Investment Income Receivable	$ 68.5				$ 65.5				68.5	65.5
Real Estate Investment [Member]
Investment Expenses:
Other Investment Expenses									11.3	11.3	18.3
Other Investment [Member]
Investment Expenses:
Other Investment Expenses									7.3	8.5	7.6
Fixed Maturities [Member]
Investment Income:
Interest and Dividends on Fixed Maturities									236.2	227.4	235.5
Equity Securities [Member]
Investment Income:
Dividends on Equity Securities									$ 32.4	$ 59.9	$ 38.0