Financial Instruments and Derivatives - Net Positions of Foreign Contracts (Detail) In Thousands, unless otherwise specified	Sep. 30, 2012 AUD	Sep. 30, 2012 CAD	Sep. 30, 2012 COP	Sep. 30, 2012 EUR (€)	Sep. 30, 2012 GBP (£)	Sep. 30, 2012 MXN	Sep. 30, 2012 NZD	Sep. 30, 2012 PLN	Sep. 30, 2012 RUB	Sep. 30, 2012 TRY
Derivative [Line Items]
Purchase (Sale) in forward contract hedge	(678)	18,745	3,846,580	€ 3,413	£ 1,663	186,246	(459)	1,153	(2,443)	2,178