Insurance Liabilities (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Change in unpaid claims
Balance at beginning of period, unpaid claims	$ 2,252.7	$ 2,130.5
Balance at beginning of period, reinsurance recoverables for unpaid claims	404.3	375.8
Net balance at beginning of period, unpaid claims	1,848.4	1,754.7
Incurred:
Incurred: Current year	653.6	617.3
Incurred: Prior years	29.0	17.9
Total incurred	682.6	635.2
Payments:
Payments: Current year	387.8	358.3
Payments: Prior years	238.1	231.8
Total payments	625.9	590.1
Net balance at end of period, unpaid claims	1,905.1	1,799.8
Balance at end of period, reinsurance recoverables for unpaid claims	403.7	388.2
Balance at end of period, unpaid claims	2,308.8	2,188.0
Amount not included in the rollforward above:
Claim adjustment expense liabilities	$ 55.1	$ 51.9