Insurance Liabilities - Future Policy Benefits and Claims (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in unpaid disability and health claims
Balance at beginning of year, Unpaid disability and health claims	$ 1,240.1	$ 1,144.7	$ 1,066.0
Incurred:
Incurred: Current year	810.2	760.5	712.0
Incurred: Prior years		1.2	1.0
Total incurred	810.2	761.7	713.0
Payments:
Payments: Current year	484.3	445.5	432.1
Payments: Prior years	243.3	220.8	202.2
Total payments	727.6	666.3	634.3
Balance at end of year:
Total balance at end of year, Unpaid disability and health claims: Current year	325.9	315.0	279.9
Total balance at end of year, Unpaid disability and health claims: Prior years	996.8	925.1	864.8
Total balance at end of year, Unpaid disability and health claims	1,322.7	1,240.1	1,144.7
Amount not included in the rollforward above:
Claim adjustment expense liabilities	51.5	47.5	43.4
Reinsurance recoverables for unpaid claims	$ 325.2	$ 304.6	$ 265.8