Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Tax expense on change in unrecognized net actuarial losses related to pension benefit plans	$ 0.2	$ 0.3	$ 0.4	$ 0.5
Tax expense on unrealized net gain on derivatives	$ 0.1	$ 0.2	$ 0.3	$ 0.2