Earnings (Loss) Per Share - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Computation Of Earnings Per Share Line Items
Net income	$ 92.9		$ 110.1		$ 41.5		$ 102.9		$ 189.6		$ 125.5		$ 263.7		$ 87.7		$ 347.4		$ 666.5		$ 522.2
Net income from continuing operations																	$ 321.7		$ 114.1		$ 178.2
Weighted average common shares outstanding
Basic (shares)																	175.8		181.7		181.3
Dilutive impact of stock options and restricted stock awards (shares)																	1.5		2.0		1.8
Diluted (shares)																	177.3		183.7		183.1
Earnings per ordinary share
Continuing operations (USD per share)	$ 0.55		$ 0.52		$ 0.44		$ 0.33		$ 0.32		$ 0.27		$ (0.02)		$ 0.07		$ 1.83		$ 0.63		$ 0.98
Discontinued operations (USD per share)	(0.01)		0.11		(0.21)		0.24		0.73		0.42		1.47		0.41		0.15		3.04		1.90
Basic earnings (loss) per common share (USD per share)	0.54	[1]	0.63	[1]	0.23	[1]	0.57	[1]	1.05	[2]	0.69	[2]	1.45	[2]	0.48	[2]	1.98	[1]	3.67	[2]	2.88
Continuing operations (USD per share)	0.54		0.52		0.44		0.32		0.30		0.27		(0.02)		0.07		1.81		0.62		0.97
Discontinued operations (USD per share)	(0.01)		0.11		(0.21)		0.25		0.74		0.41		1.45		0.41		0.15		3.01		1.88
Diluted earnings (loss) per common share (USD per share)	$ 0.53	[1]	$ 0.63	[1]	$ 0.23	[1]	$ 0.57	[1]	$ 1.04	[2]	$ 0.68	[2]	$ 1.43	[2]	$ 0.48	[2]	$ 1.96	[1]	$ 3.63	[2]	$ 2.85
Anti-dilutive stock options excluded from the calculation of diluted earnings per share																	1.2		1.8		1.2
Retained earnings
Computation Of Earnings Per Share Line Items
Net income																	$ 347.4		$ 666.5		$ 522.2

[1] (2) 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.

[2] (3) 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.