Restructuring (Narrative) (Details) $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 employee	Dec. 31, 2018 USD ($) employee
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 2.9	$ 0.8		$ 7.2
Other costs related to repositioning actions	2.1			7.5
Effect on future earnings, amount	30.0
Restructuring and related cost, expected cost remaining	8.9
Acquisition-Related Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2.2			$ 1.6
Restructuring and related cost, expected number of positions eliminated | employee				170
Restructuring and related cost, number of positions eliminated, period percent				2.00%
Severance costs	0.2
Other restructuring costs	2.0
Other costs related to repositioning actions	2.4
Effect on future earnings, amount	23.0
2017Repositioning [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.7
Restructuring and related cost, expected number of positions eliminated | employee			300
Restructuring and related cost, number of positions eliminated, period percent			3.00%
Severance costs	0.6
Other restructuring costs	0.1
2017Repositioning [Member] | cumulative [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	30.4
Severance costs	30.9
Other restructuring costs	$ (0.5)