Insurance Liabilities - Discounting Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Carrying amount of liabilities for unpaid claims	$ 1,151.5
Aggregate amount of discount	215.0
Long-Term Disability/Group Life Waiver
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Carrying amount of liabilities for unpaid claims	1,029.9	$ 1,020.0
Aggregate amount of discount	215.0	217.7
Interest accretion	$ 34.2	$ 34.5	$ 35.0
Long-Term Disability/Group Life Waiver | Minimum
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Discount rate	3.30%	3.30%
Long-Term Disability/Group Life Waiver | Maximum
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Discount rate	7.00%	7.00%
Dental/Vision/Short-Term Disability/Critical Illness/Accident
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Carrying amount of liabilities for unpaid claims	$ 71.2	$ 59.3
Group Life
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Carrying amount of liabilities for unpaid claims	$ 50.4	$ 49.7