Long-term Debt - Long-term Debt (Parenthetical) (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
3.30% Senior Notes due 2021 [Member]
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	3.30%	3.30%
Debt instrument maturity date	2021	2021
4.50% Guaranteed Notes due 2014 [Member]
Proforma Debt Instrument [Line Items]
Debt instrument interest rate		4.50%
Debt instrument maturity date		2014
2.75% Guaranteed Notes due 2015 [Member]
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	2.75%	2.75%
Debt instrument maturity date	2015	2015
1.95% Senior Notes due 2016 [Member]
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	1.95%	1.95%
Debt instrument maturity date	2016	2016
4.20% Senior Notes due 2021 [Member]
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	4.20%	4.20%
Debt instrument maturity date	2021	2021
1.25% Senior Notes due 2017 [Member]
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	1.25%	1.25%
Debt instrument maturity date	2017	2017
2.40% Senior Notes due 2022 [Member]
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	2.40%	2.40%
Debt instrument maturity date	2022	2022
2.65% Senior Notes due 2016 [Member]
Proforma Debt Instrument [Line Items]
Debt instrument interest rate	2.65%	2.65%
Debt instrument maturity date	2016	2016
Floating Rate Senior Notes due 2014 [Member]
Proforma Debt Instrument [Line Items]
Debt instrument maturity date	2014	2014