Long-Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Debt Disclosure [Line Items]
Long-term debt non current	$ 1,409,600	$ 908,700
1.375% Notes Due 2018
Debt Disclosure [Line Items]
Long-term debt non current	499,400
4.40% Notes Due 2021
Debt Disclosure [Line Items]
Long-term debt non current	497,100	496,800
2.875% Notes Due 2016
Debt Disclosure [Line Items]
Long-term debt non current	263,300	262,100
6.70% Notes Due 2026
Debt Disclosure [Line Items]
Long-term debt non current	$ 149,800	$ 149,800