Insurance Liabilities (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Change in unpaid claims
Balance at beginning of period, unpaid claims	$ 2,001.3	$ 1,872.2
Balance at beginning of period, reinsurance recoverables for unpaid claims	340.3	314.1
Net balance at beginning of period, unpaid claims	1,661.0	1,558.1
Incurred:
Incurred: Current year	591.6	543.7
Incurred: Prior years	23.9	14.1
Total incurred	615.5	557.8
Payments:
Payments: Current year	343.4	311.2
Payments: Prior years	225.9	200.5
Total payments	569.3	511.7
Net balance at end of period, unpaid claims	1,707.2	1,604.2
Balance at end of period, reinsurance recoverables for unpaid claims	356.1	321.7
Balance at end of period, unpaid claims	2,063.3	1,925.9
Amount not included in the rollforward above:
Claim adjustment expense liabilities	$ 50.3	$ 60.8