Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Parenthetical) (Detail)	Sep. 30, 2013
2.875% Senior notes due October 1, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate of debt	2.875%
2.875% Senior notes due October 1, 2022 | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate of debt	2.875%
3.35% Senior Notes Due December 15, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate of debt	3.35%
3.35% Senior Notes Due December 15, 2015 | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate of debt	3.35%