Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Cash Flow, Supplemental [Line Items]
Cash paid for interest, net	$ 107.2	$ 143.4	$ 76.9
Cash paid for income taxes, net	$ 362.1	$ 145.1	$ 182.8