Summary of Significant Accounting Policies - Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Aug. 03, 2018	Jul. 28, 2016	Oct. 29, 2015
Equity, Class of Treasury Stock [Line Items]
Shares authorized to be repurchased (in shares)				6,000,000.0	6,000,000.0	6,000,000.0
Shares repurchased (in shares)	5,700,000	1,900,000	6,600,000
Total cost of shares repurchased	$ 500.7	$ 203.9	$ 482.2
Dividends declared (in dollars per share)	$ 2.02	$ 1.86	$ 1.72
Total dividend payments	$ 127.3	$ 123.7	$ 118.4
Net earnings, net of tax, attributable to noncontrolling interests	$ (4.9)	$ 6.5	$ 10.1
August 2018 Authorization
Equity, Class of Treasury Stock [Line Items]
Shares repurchased (in shares)	2,900,000
Shares remaining authorized for repurchase (in shares)	3,100,000
July 2016 Authorization
Equity, Class of Treasury Stock [Line Items]
Shares repurchased (in shares)	2,800,000	1,900,000	1,300,000
Shares remaining authorized for repurchase (in shares)	0
2015 Authorization
Equity, Class of Treasury Stock [Line Items]
Shares repurchased (in shares)			5,300,000
Shares remaining authorized for repurchase (in shares)	0