Commitments and Contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Commitments And Contingent Liabilities [Line Items]
Balance at the beginning of the year	$ 122.7
Additions charged to expense, net	0.3
Payments, net	(0.8)
Balance at the end of period	122.2
Amounts recognized in our Condensed Consolidated Balance Sheet at the end of the period:
Current liabilities	9.2	9.1
Noncurrent liabilities	113.0	113.6
Total	$ 122.2