Earnings (Loss) Per Share - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended														12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016	Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Computation Of Earnings Per Share Line Items
Net income (loss)	$ 189.6	$ 125.4		$ 263.7		$ 87.8		$ 131.0	$ 141.0		$ 142.8		$ 107.4		$ 666.5	$ 522.2	$ (76.4)
Net income from continuing operations															$ 480.0	$ 451.6	$ 397.1
Weighted average common shares outstanding
Basic (shares)															181.7	181.3	180.3
Dilutive impact of stock options and restricted stock awards (shares)															2.0	1.8	2.3
Diluted (shares)															183.7	183.1	182.6
Earnings (loss) per ordinary share
Income (Loss) from Continuing Operations, Per Basic Share	$ 1.12	$ 0.70		$ 0.38		$ 0.44		$ 0.60	$ 0.65		$ 0.73		$ 0.50		$ 2.64	$ 2.49	$ 2.20
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	(0.07)	(0.01)		1.07		0.04		0.12	0.13		0.06		0.09		1.03	0.39	(2.62)
Basic earnings (loss) per common share (USD per share)	1.05	0.69	[1]	1.45	[1]	0.48	[1]	0.72	0.78	[1]	0.79	[1]	0.59	[1]	3.67	2.88	(0.42)
Income (Loss) from Continuing Operations, Per Diluted Share	1.11	0.69		0.37		0.44		0.60	0.64		0.73		0.50		2.61	2.47	2.17
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	(0.07)	(0.01)		1.06		0.04		0.11	0.13		0.05		0.09		1.02	0.38	(2.59)
Diluted earnings (loss) per common share (USD per share)	$ 1.04	$ 0.68	[1]	$ 1.43	[1]	$ 0.48	[1]	$ 0.71	$ 0.77	[1]	$ 0.78	[1]	$ 0.59	[1]	$ 3.63	$ 2.85	$ (0.42)
Anti-dilutive stock options excluded from the calculation of diluted earnings per share															1.8	1.2	1.3

[1] Amounts may not total to annual earnings because each quarter and year are calculated separately based on basic and diluted weighted-average ordinary shares outstanding during that period.