Long-Term Debt (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
1.25% Notes due on May 19, 2014
Debt Instrument [Line Items]
Long-term debt, interest rate	1.25%	1.25%
Long-term debt, maturity date	May 19, 2014	May 19, 2014
2.125% Notes due on May 19, 2016
Debt Instrument [Line Items]
Long-term debt, interest rate	2.125%	2.125%
Long-term debt, maturity date	May 19, 2016	May 19, 2016
3.625% Notes due on May 19, 2021
Debt Instrument [Line Items]
Long-term debt, interest rate	3.625%	3.625%
Long-term debt, maturity date	May 19, 2021	May 19, 2021