- Schedule of Long-Term Debt (Parenthetical) (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013
$1 billion revolver weighted average rate 1.53%, due in 2016
Debt Instrument [Line Items]
Maximum borrowing capacity of line of credit facility	1,000,000,000
Interest rate percentage	1.53%
$100 million Private Placement notes 5.64%, due in 2015
Debt Instrument [Line Items]
Long-term debt, face amount	100,000,000
Interest rate percentage	5.64%
$175 million Private Placement notes 3.89%, due in 2017
Debt Instrument [Line Items]
Long-term debt, face amount	175,000,000
Interest rate percentage	3.89%
$125 million Private Placement notes 2.68%, due in 2019
Debt Instrument [Line Items]
Long-term debt, face amount	125,000,000
Interest rate percentage	2.68%
$225 million Private Placement notes 4.47%, due in 2020
Debt Instrument [Line Items]
Long-term debt, face amount	225,000,000
Interest rate percentage	4.47%
$125 million Private Placement notes 3.26%, due in 2022
Debt Instrument [Line Items]
Long-term debt, face amount	125,000,000
Interest rate percentage	3.26%
Acquisition notes weighted average rate of 2.58% and weighted average maturity of 3.6 years
Debt Instrument [Line Items]
Interest rate percentage	2.58%
Debt, maturity period	3 years 7 months 6 days
Foreign bank debt weighted average rate 4.93% and weighted average maturity of 1.7 years
Debt Instrument [Line Items]
Interest rate percentage	4.93%
Debt, maturity period	1 year 8 months 12 days