Stock-based Compensation (Details) (Restricted Stock Plan, USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended					1 Months Ended
	Mar. 31, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2012 Employee	Sep. 30, 2012 Non-Employee Director	Aug. 31, 2012 Key Employees and Non-Employee Directors	Dec. 30, 2011 Key Employees and Non-Employee Directors	Nov. 30, 2011 Key Employees and Non-Employee Directors
Stock-Based Compensation
Number of shares of common stock reserved for issuance		400,000
Award vesting period					3 years	3 years
Period of performance goal based on net income used for determination of vesting period					3 years
Restricted stock plan activity, number of shares
Unvested at beginning of the period (in shares)		126,000
Granted (in shares)		31,600					1,000	3,000	27,600
Forfeited / Canceled (in shares)		(25,600)
Vested (in shares)		(21,000)
Unvested at end of the period (in shares)		111,000	126,000
Expected to vest (in shares)		111,000
Restricted stock plan activity, Weighted Average Fair Value at Grant Date
Unvested at beginning of the period (in dollars per share)		$ 29.86
Granted (in dollars per share)		$ 55.90					$ 48.19	$ 58.64	$ 55.88
Forfeited / Canceled (in dollars per share)		$ 17.82
Vested (in dollars per share)		$ 17.82
Unvested at end of the period (in dollars per share)		$ 42.32	$ 29.86
Expected to vest (in dollars per share)		$ 42.32
Restricted stock plan activity, other disclosures
Compensation expense		$ 1,518	$ 992	$ 516
Remaining unrecognized compensation expense		$ 1,983
Weighted average period for recognition		1 year 4 months 28 days
Compensation expense not recorded on shares due to performance goal not achieved	25,600