Debt and Credit Facilities - Lines of credit (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Line Of Credit [Line Items]
Used lines of credit	$ 39.2	$ 34.5
Unused lines of credit	989.5	1,028.7
Total available lines of credit	1,028.7	1,063.2
Accounts receivable securitization program - committed	112.0	92.0
Committed line of credit facilities [Member]
Line Of Credit [Line Items]
Total available lines of credit	700.5	703.9
Uncommitted line of credit facilities [Member]
Line Of Credit [Line Items]
Total available lines of credit	$ 328.2	$ 359.3