Consolidated Statement of Comprehensive Income Parentheticals - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Unrealized Loss on Securities, Income Tax Benefit	$ (0.2)	$ (0.3)	$ (0.2)
Unrealized Gain on Derivatives, Income Tax Expense	0.0	0.1	0.1
Defined Benefit Pension and Other Postretirement Benefit Plans, Income Tax Benefit	$ (2.4)	$ (2.2)	$ (2.8)