Stockholders' Equity (Capital Stock Activity) (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ordinary shares, shares outstanding (in shares)	450.5	465.1
Ordinary Shares Issued
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ordinary shares, shares outstanding (in shares)	450.5	465.1	119.2	119.0
Stock Issued During Period, Shares, Acquisitions		347.4
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures	0.2	0.6	0.2
Common Stock Dividends, Shares			3.2
Treasury Stock, Shares, Retired	(14.8)	(2.1)	(3.2)
Ordinary Shares Held in Employee Benefit Trust
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ordinary shares, shares outstanding (in shares)	0.1	0.1
Stock Issued During Period, Shares, New Issues		0.1
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ordinary shares, shares outstanding (in shares)			0.3	0.8
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			(0.4)
Stock Repurchased and Retired During Period, Shares		0.3
Treasury Stock, Shares, Acquired	14.8	2.1	3.2
Shares Acquired Pursuant to Liquidity Contract			1.3
Shares Sold Pursuant to Liquidity Contract			1.4
Treasury Stock, Shares, Retired	(14.8)	(2.1)	(3.2)