Long-term Debt - Long-term Debt (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
3.30% Senior Notes due 2021
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	3.30%	3.30%
Debt instrument maturity date	2021
3.65% Senior Notes due 2023
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	3.65%	3.65%
Debt instrument maturity date	2023
2.75% Guaranteed Notes due 2015
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	2.75%	2.75%
Debt instrument maturity date	2015
1.95% Senior Notes due 2016
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	1.95%	1.95%
Debt instrument maturity date	2016
4.20% Senior Notes due 2021
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	4.20%	4.20%
Debt instrument maturity date	2021
1.25% Senior Notes due 2017
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	1.25%	1.25%
Debt instrument maturity date	2017
2.40% Senior Notes due 2022
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	2.40%	2.40%
Debt instrument maturity date	2022
1.50% Guaranteed Notes due 2019
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	1.50%	1.50%
Debt instrument maturity date	2019
2.65% Senior Notes due 2016
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	2.65%	2.65%
Debt instrument maturity date	2016