Segment Reporting - Reconciliation of Segment Assets to Total Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total assets	$ 4,148.5	$ 3,939.7
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total assets	3,048.4	2,914.6
Assets of Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Total assets	$ 1,100.1	$ 1,025.1