Other noncurrent liabilities - Other Noncurrent Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Other Liabilities Disclosure [Abstract]
Reserve for uncertain tax positions	$ 31.2	$ 29.4
Asset retirement obligations	24.2	23.8
Insurance claims and expenses	9.7	9.7
Employee benefits	10.8	11.3
Deferred income	1.0	1.0
Other	3.2	3.1
Total	$ 80.1	$ 78.3