Long-Term Debt (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
$1 billion revolver weighted average rate 1.71%, due in 2016
Debt Instrument [Line Items]
Interest rate percentage	1.71%	1.71%
Maximum borrowing capacity of line of credit facility	$ 1,000	$ 1,000
$100 million Private Placement notes 5.64%, due in 2015
Debt Instrument [Line Items]
Long-term debt, face amount	100.0	100.0
Interest rate percentage	5.64%	5.64%
$200 million Term Loan with rate of 1.09% due Dec 2012
Debt Instrument [Line Items]
Long-term debt, face amount	200.0
Interest rate percentage	1.09%
$175 million Private Placement notes 3.89%, due in 2017
Debt Instrument [Line Items]
Long-term debt, face amount	175.0	175.0
Interest rate percentage	3.89%	3.89%
$225 million Private Placement notes 4.47%, due in 2020
Debt Instrument [Line Items]
Long-term debt, face amount	$ 225.0	$ 225.0
Interest rate percentage	4.47%	4.47%
Acquisition notes weighted average rate of 2.96% and weighted average maturity of 3.9 years
Debt Instrument [Line Items]
Debt, maturity period	3 years 10 months 24 days	3 years 10 months 24 days
Interest rate percentage	2.96%	2.96%
Foreign bank debt weighted average rate 5.94% and Weighted average maturity of 2.0 years
Debt Instrument [Line Items]
Debt, maturity period	2 years	2 years
Interest rate percentage	5.94%	5.94%