Consolidated Statements of Earnings and Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net gain (loss) from discontinued operations, net of tax (benefit) expense	$ 3.6	$ (0.8)	$ 34.6
(Loss) gain on disposal of discontinued business, net of tax (benefit)	$ (4.1)	$ (15.2)	$ (41.8)