Accounts Receivable - Transactions Affecting Allowance for Doubtful Accounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Balance, beginning of year	$ 26.0	$ 27.0	$ 28.3
Provisions charged to expense	12.1	17.8	14.9
Write-offs and other	(2.2)	(18.8)	(16.2)
Balance, end of year	$ 35.9	$ 26.0	$ 27.0