Earnings Per Share - Schedule of Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Basic earnings per share
Net income from continuing operations	$ 73.7	$ 63.8
Amount allocated to nonvested participating shareholders	(0.1)	(0.2)
Income before discontinued operations available to common shareholders - Basic	73.6	63.6
Income (loss) from discontinued operations, net	0.1	(5.8)
Amount allocated to nonvested participating shareholders	0.0	0.0
Income (loss) from discontinued operations available to common shareholders - Basic	0.1	(5.8)
Net income	73.8	58.0
Amount allocated to nonvested participating shareholders	(0.1)	(0.2)
Net income available to common shareholders - Basic	$ 73.7	$ 57.8
Average common shares outstanding - Basic	234.0	232.8
Earnings per share from continuing operations available to common shareholders - Basic	$ 0.31	$ 0.27
Earnings per share from discontinued operations available to common shareholders - Basic	0.00	(0.02)
Earnings per share - Basic	$ 0.31	$ 0.25
Diluted earnings per share
Net income from continuing operations	$ 73.7	$ 63.8
Amount allocated to nonvested participating shareholders	(0.1)	(0.2)
Income before discontinued operations available to common shareholders - Diluted	73.6	63.6
Income (loss) from discontinued operations, net	0.1	(5.8)
Amount allocated to nonvested participating shareholders	0.0	0.0
Income (loss) from discontinued operations available to common shareholders - Diluted	0.1	(5.8)
Net income	73.8	58.0
Amount allocated to nonvested participating shareholders	(0.1)	(0.2)
Net income available to common shareholders - Diluted	$ 73.7	$ 57.8
Average common shares outstanding - Basic	234.0	232.8
Assumed conversion of stock options, unvested restricted stock, unvested RSUs and contingent performance shares, net	1.2	0.7
Average common shares outstanding - Diluted	235.2	233.5
Earnings per share from continuing operations available to common shareholders - Diluted	$ 0.31	$ 0.27
Earnings per share from discontinued operations available to common shareholders - Diluted	0.00	(0.02)
Earnings per share - Diluted	$ 0.31	$ 0.25
Anti-dilutive shares	0.2	0.1