Shareholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 1,407.8	$ 1,246.6
Cumulative effect of an accounting change						$ 12.2
Total stockholders’ equity, beginning balance	$ 1,405.9	$ 1,391.5	1,407.8	1,246.6	$ 1,420.0	1,407.8
Net income	77.1	(18.9)	148.1	47.0
Other comprehensive loss, net of tax	(109.7)	31.4	(59.7)	72.9
Recognition of stock-based compensation			18.1	21.3
Exercise of stock options			11.1	12.9
Treasury share repurchases			(103.8)	(8.3)
Non-controlling interests of acquired subsidiaries			(26.9)
Dividends paid to noncontrolling interests			(1.0)	(0.9)
Ending balance	1,405.9	1,391.5	1,405.9	1,391.5
Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			1,276.1	1,125.1
Cumulative effect of an accounting change						12.1
Total stockholders’ equity, beginning balance	1,303.5	1,266.2	1,276.1	1,125.1	1,288.2	1,276.1
Net income			144.8	43.3
Other comprehensive loss, net of tax			(57.8)	71.9
Recognition of stock-based compensation			18.1	21.3
Exercise of stock options			11.1	12.9
Treasury share repurchases			(103.8)	(8.3)
Non-controlling interests of acquired subsidiaries			2.9
Dividends paid to noncontrolling interests			0.0	0.0
Ending balance	1,303.5	1,266.2	1,303.5	1,266.2
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			131.7	121.5
Cumulative effect of an accounting change						0.1
Total stockholders’ equity, beginning balance	102.4	125.3	131.7	121.5	$ 131.8	$ 131.7
Net income			3.3	3.7
Other comprehensive loss, net of tax			(1.9)	1.0
Recognition of stock-based compensation			0.0	0.0
Exercise of stock options			0.0	0.0
Treasury share repurchases			0.0	0.0
Non-controlling interests of acquired subsidiaries			(29.8)
Dividends paid to noncontrolling interests			(1.0)	(0.9)
Ending balance	$ 102.4	$ 125.3	$ 102.4	$ 125.3