Commitments and Contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Commitments And Contingent Liabilities [Line Items]
Balance at the beginning of the period	$ 122.7
Additions charged to expense, net	6.1
Payments, net	(2.0)
Balance at the end of period	126.8
Amounts recognized in our Condensed Consolidated Balance Sheet at the end of the period:
Current liabilities	16.5	9.1
Noncurrent liabilities	110.3	113.6
Total	$ 126.8