Stock Option Activity and Related Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
	Mar. 31, 2012	Mar. 31, 2012
Number of Options
Beginning balance		11,866
Options granted		0
Options assumed	41	41
Options cancelled		(22)
Options exercised		(3,243)
Ending balance	8,642	8,642
Exercisable at end of the period	8,436	8,436
Expected to vest after end of the period	206	206
Weighted-Average Exercise Price
Beginning balance		$ 108.64
Options granted		$ 0
Options assumed	$ 30.92	$ 30.92
Options cancelled		$ 102.91
Options exercised		$ 85.54
Ending balance	$ 116.95	$ 116.95
Exercisable at end of the period	$ 116.67	$ 116.67
Expected to vest after end of the period	$ 128.57	$ 128.57
Weighted - Average Remaining Contractual Term (in years)
Ending balance (in years)		2 years 44 days
Exercisable at end of the period (in years)		2 years 22 days
Expected to vest after end of the period (in years)		4 years 142 days
Aggregate Intrinsic Value
Ending balance	$ 4,170,553	$ 4,170,553
Exercisable at end of the period	4,073,404	4,073,404
Expected to vest after end of the period	$ 97,150	$ 97,150