Stockholders' Equity (Details 6) (USD $)	12 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Weighted-Average Fair Value
Stock-based compensation	$ 13,379,000	$ 12,117,000	$ 9,136,000
Unvested awards
Costs related to unvested awards, not yet recognized	$ 38,312,000
Weighted average vesting period for recognition of cost related to unvested awards	27 months
Restricted shares
Restricted share activity
Unvested restricted shares at the beginning of the period	1,399,609	1,294,082
Restricted shares granted	997,857	633,647	736,340	699,410
Restricted shares vested	(450,514)	(390,068)
Restricted shares cancelled	(403,083)	(138,052)	(150,112)	(45,026)
Unvested restricted shares at the end of the period	1,543,869	1,399,609	1,294,082
Weighted-Average Fair Value
Unvested restricted shares at the beginning of the period (in dollars per share)	$ 22.51	$ 13.13
Restricted shares granted (in dollars per share)	$ 36.97	$ 34.05
Restricted shares vested (in dollars per share)	$ 21.18	$ 12.53
Restricted shares cancelled (in dollars per share)	$ 35.89	$ 15.70
Unvested restricted shares at the end of the period (in dollars per share)	$ 28.89	$ 22.51	$ 13.13

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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