Summary of Significant Accounting Policies (Changes in Product Warranty Liability) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in product warranty liability
Balance at January 1	$ 7.1	$ 6.1	$ 6.9
Claims paid during the year	(4.0)	(3.7)	(4.7)
Warranty expense	4.7	2.0	4.0
Acquired warranty liabilities	0.1	2.8	0.0
Other	0.0	(0.1)	(0.1)
Balance at December 31	$ 7.9	$ 7.1	$ 6.1