Consolidated Statement of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent, Parenthetical Disclosures [Abstract]
Adjustment to pension and other benefit plans tax impact	$ 18.9	$ 10.7	$ 33.9
Unrealized gain or loss on investment tax impact	0.1	0.2	0.0
Unrealized gain or loss on cash flow hedge tax impact	$ 0.5	$ (0.3)	$ (0.1)