Stock-Based Compensation Plans - Additional Information (Detail) (USD $)	12 Months Ended											12 Months Ended		0 Months Ended	3 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended			12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2010	Sep. 30, 2014 Maximum [Member]	Sep. 30, 2014 Minimum [Member]	Sep. 30, 2014 1999 Employee Stock Purchase Plan [Member]	Sep. 30, 2013 1999 Employee Stock Purchase Plan [Member]	Sep. 30, 2014 1999 Employee Stock Purchase Plan [Member] Maximum [Member]	Sep. 30, 2012 1999 Employee Stock Purchase Plan [Member] Maximum [Member]	Sep. 30, 2013 1999 Employee Stock Purchase Plan [Member] Maximum [Member]	Sep. 30, 2014 2009 Equity Incentive Plan [Member]	Sep. 30, 2013 2009 Equity Incentive Plan [Member]	Feb. 28, 2014 Former Chairman of the Board [Member]	Mar. 31, 2014 Director [Member]	Sep. 30, 2014 Fiscal 2014 (2014 - 2016) [Member]	Sep. 30, 2014 Fiscal 2013 (2013 - 2015) [Member]	Sep. 30, 2014 Fiscal 2012 (2012 - 2014) [Member]	Dec. 31, 2014 Fiscal 2012 (2012 - 2014) [Member] Subsequent Event [Member]	Sep. 30, 2014 Fiscal 2011 (2011 - 2013) [Member]	Dec. 31, 2013 Performance Shares [Member]	Sep. 30, 2010 Performance Shares [Member]	Dec. 31, 2014 Performance Shares [Member] Subsequent Event [Member]	Dec. 31, 2013 Performance Shares [Member] Maximum [Member]	Dec. 31, 2014 Performance Shares [Member] Maximum [Member] Subsequent Event [Member]	Sep. 30, 2014 Performance Shares [Member] Fiscal 2014 (2014 - 2016) [Member]	Sep. 30, 2014 Performance Shares [Member] Fiscal 2013 (2013 - 2015) [Member]	Sep. 30, 2014 Performance Shares [Member] Fiscal 2012 (2012 - 2014) [Member]	Sep. 30, 2014 Nonqualified Stock Options [Member]	Sep. 30, 2014 Nonqualified Stock Options [Member] Granted prior to May 2008 [Member]	Sep. 30, 2014 Nonqualified Stock Options [Member] Board Of Director [Member]	Sep. 30, 2014 Nonqualified Stock Options [Member] Board Of Director [Member] Maximum [Member]	Sep. 30, 2014 Nonqualified Stock Options [Member] Board Of Director [Member] Minimum [Member]	Sep. 30, 2014 Nonqualified Stock Options [Member] Employee [Member] Granted subsequent to April 2008 [Member]	Sep. 30, 2014 Restricted Stock Units (RSUs) [Member] 2009 Equity Incentive Plan [Member]	Sep. 30, 2013 Restricted Stock Units (RSUs) [Member] 2009 Equity Incentive Plan [Member]	Sep. 30, 2014 Deferred Stock Units [Member] Director [Member] 2009 Equity Incentive Plan [Member]
Stock Based Compensation Activity [Line Items]
Unrecognized compensation costs related to non-vested awards	$ 2,000,000
Weighted average period for recognition of compensation costs related to non-vested awards	1 year 4 months 24 days
Performance share awards fully expensed	200,000
Weighted average per share fair value of stock options	$ 8.72	$ 8.69	$ 5.26
Dividend yield	0.00%	0.00%	0.00%
Stock option expiration term upon expiration of employment or service																																10 years	7 years
Vesting percentage																														20.00%				25.00%
Vesting terms																														Non-qualified stock options granted prior to May 2008 generally become exercisable with respect to 20% of the shares on each of the first five anniversaries following the grant date	The Company modified non-qualified stock option awards granted to Board members in February 2014, which resulted in acceleration of the stock option vesting period. The modification changed the vesting period to a pro-rata basis over a one-year period from a four-year period and resulted in an increase to stock option expense of $0.5 million in fiscal 2014.			Non-qualified stock options granted to the Company's employees subsequent to April 2008 generally become exercisable with respect to 25% of the shares on each of the first four anniversaries following the grant date
Stock option related expense																													500,000
Number of authorized shares in 2009 plan												1,500,000
Number of shares available for future awards												1,134,186
Aggregate intrinsic value of the option shares outstanding	3,500,000
Aggregate intrinsic value of the option shares exercisable	2,600,000
Remaining contractual life of options outstanding	3 years 6 months
Remaining contractual life of options exercisable	2 years 10 months 24 days
Total pre-tax intrinsic value of options exercised	1,400,000	100,000
Restricted stock expense	200,000	100,000	200,000											200,000																					200,000
Performance period start year																2014	2013	2012		2011
Performance period end year																2016	2015	2014		2013
Performance Shares, time period	3 years	3 years	3 years	3 years
Performance share awards, estimated vesting percentage					200.00%	20.00%
Issuance of shares																					122,053		98,870	137,066	124,994
Expenses recognized related to Performance Shares	600,000	1,200,000	1,000,000	0
Number of Performance Shares																						4,373													24,834	24,834	12,843
Fair value of performance shares for grants awarded																										900,000	900,000	800,000
Maximum Shares																			98,093
Common stock authorized, shares									400,000
Annual compensation withheld									10.00%
Annual compensation withheld, maximum limit							25,000
Employee contributions									100,000		100,000
Stock compensation expenses recognized							100,000	100,000		100,000
Number of stock units forfeited																																			3,417
Stock based compensation expenses	3,337,000	2,552,000	2,671,000												900,000																				400,000	100,000
Number of deferred stock units issued value																																					242,000
DSU expenses												$ 100,000	$ 100,000