Shareholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total stockholders’ equity, beginning balance	$ 1,407.8	$ 1,246.6
Cumulative effect of an accounting change			$ 12.2
Stockholders' equity, adjusted balance			1,420.0
Net income	71.0	65.9
Other comprehensive income, net of tax	50.0	41.5
Recognition of stock-based compensation	8.4	10.4
Exercise of stock options	6.2	8.8
Treasury stock repurchase	(3.3)
Noncontrolling interests of acquired subsidiaries	(26.9)
Dividends paid to noncontrolling interests	(1.0)	(0.4)
Total stockholders’ equity, ending balance	1,524.4	1,372.8
Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total stockholders’ equity, beginning balance	1,276.1	1,125.1
Cumulative effect of an accounting change			12.1
Stockholders' equity, adjusted balance			1,288.2
Net income	69.9	64.1
Other comprehensive income, net of tax	49.1	40.6
Recognition of stock-based compensation	8.4	10.4
Exercise of stock options	6.2	8.8
Treasury stock repurchase	(3.3)
Noncontrolling interests of acquired subsidiaries	2.9
Dividends paid to noncontrolling interests	0.0	0.0
Total stockholders’ equity, ending balance	1,421.4	1,249.0
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total stockholders’ equity, beginning balance	131.7	121.5
Cumulative effect of an accounting change			0.1
Stockholders' equity, adjusted balance			$ 131.8
Net income	1.1	1.8
Other comprehensive income, net of tax	0.9	0.9
Recognition of stock-based compensation	0.0	0.0
Exercise of stock options	0.0	0.0
Treasury stock repurchase	0.0
Noncontrolling interests of acquired subsidiaries	(29.8)
Dividends paid to noncontrolling interests	(1.0)	(0.4)
Total stockholders’ equity, ending balance	$ 103.0	$ 123.8