Financial Instruments and Fair Value Measurements - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Remaining cash equivalents	$ 698,059		$ 605,536
Maturity period of cash equivalents at the time of purchase	Three months or less
Maturity period of instruments in short-term investments	Three months and less than one year
Fair value of long-term debt	4,314,668		4,317,059
Transfer of assets in and out of level 1, 2 and 3 measurements during the period	0	0
Transfer of liabilities in and out of level 1, 2 and 3 measurements during the period	0	0
4.55% Notes Due 2013 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt	200,000		200,000
Debt instrument, interest rate	4.55%		4.55%
Fair value of debt reclassified from long term to short term	$ 202,352		$ 206,452