Consolidated Statement of Comprehensive Income Parentheticals - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Unrealized Gain on Securities, Income Tax Expense	$ 0.2	$ 0.3	$ 0.5	$ 0.0
Defined Benefit Pension and Other Postretirement Benefit Plans, Income Tax Expense	$ 0.2	$ 0.1	$ 0.3	$ 0.2