Long-Term Debt (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
$1 billion revolver weighted average rate 1.62%, due in 2016
Debt Instrument [Line Items]
Interest rate percentage	1.62%	1.62%
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%
$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%
$125 million Private Placements notes 2.68% due in 2019
Debt Instrument [Line Items]
Long-term debt, face amount	125.0
Interest rate percentage	2.68%
$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%
$125 million Private Placements notes 3.26% due in 2022
Debt Instrument [Line Items]
Long-term debt, face amount	$ 125.0
Interest rate percentage	3.26%
Acquisition notes weighted average rate of 2.60% and weighted average maturity of 3.8 years
Debt Instrument [Line Items]
Interest rate percentage	2.60%
Debt, maturity period	3 years 9 months 18 days
Foreign bank debt weighted average rate 5.83% and Weighted average maturity of 2.0 years
Debt Instrument [Line Items]
Interest rate percentage	5.83%
Debt, maturity period	2 years