Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Liability, Provisional Income Tax (Expense) Benefit	$ 10.5
Current Income Tax Expense (Benefit)	23.1	$ (8.2)	$ 25.7
Interest on income taxes expense			(3.3)
Income Taxes Paid, Net	(13.0)	$ 0.5	$ (44.4)
Mutual Savings Life [Member]
Current Income Tax Expense (Benefit)	3.1
Mutual Savings Life’s income	$ 14.7