Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Amortization of prior service credit, tax	$ 0.1	$ 0.1	$ 0.2	$ 0.2
Amortization of actuarial net losses, tax	$ (0.2)	$ (0.2)	$ (0.8)	$ (0.8)