Stock-Based Compensation Plans - Additional Information (Detail) (USD $)	12 Months Ended								1 Months Ended	3 Months Ended			12 Months Ended							1 Months Ended	3 Months Ended	12 Months Ended	1 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2013 Fiscal 2011 - 2013 [Member]	Sep. 30, 2013 Fiscal 2012 - 2014 [Member]	Sep. 30, 2013 Fiscal 2013 - 2015 [Member]	Sep. 30, 2013 Equity Incentive Plan 2009 [Member]	Sep. 30, 2000 Maximum [Member]	Sep. 30, 2013 Maximum [Member]	Sep. 30, 2012 Maximum [Member]	Sep. 30, 2011 Maximum [Member]	Sep. 30, 2013 Maximum [Member]	Sep. 30, 2013 Minimum [Member]	Sep. 30, 2013 Incentive Stock Option [Member]	Sep. 30, 2013 Performance Shares [Member]	Sep. 30, 2012 Performance Shares [Member]	Sep. 30, 2011 Performance Shares [Member]	Sep. 30, 2010 Performance Shares [Member]	Dec. 12, 2012 Restricted Stock Units (RSUs) [Member]	Sep. 30, 2013 Restricted Stock Units (RSUs) [Member]	Sep. 30, 2013 Fiscal 2011 - 2013 [Member]	Nov. 30, 2013 Fiscal 2011 - 2013 [Member] Subsequent Event [Member]
Stock Based Compensation Activity [Line Items]
Unrecognized compensation costs related to non-vested awards	$ 3,400,000
Weighted average period for recognition of compensation costs related to non-vested awards	2 years 7 months 6 days
Performance Share Awards Fully Expensed	1,200,000
Weighted average per share fair value of stock options	$ 8.69	$ 5.26	$ 3.96
Dividend yield	0.00%	0.00%	0.00%
Incentive stock options granted price minimum percentage															100.00%
Incentive stock options granted price maximum percentage															110.00%
Combined voting power minimum	10.00%
Incentive stock options exercisable rate															20.00%
Percentage of non qualified stock options on each of first five anniversaries	20.00%
Percentage of non qualified stock options on each of first four anniversaries	25.00%
Number of authorized shares in 2009 plan								1,500,000
Number of shares available for future awards								1,267,000
Aggregate intrinsic value of the option shares outstanding	6,000,000
Aggregate intrinsic value of the option shares exercisable	2,500,000
Remaining contractual life of options outstanding	3 years 10 months 24 days
Remaining contractual life of options exercisable	3 years 1 month 6 days
Total pre-tax intrinsic value of options exercised	0.1	0.1
Common stock options exercised, Shares	10,273	11,379	0
Restricted stock expense	100,000	200,000	600,000
Expenses recognized related to Performance Shares	1,200,000	1,000,000	200,000	0
Performance Shares, time period	3 years	3 years	3 years
Performance share awards, estimated vesting percentage													200.00%	20.00%
Number of Performance Shares																		68,533	4,373	11,776	5,932
Performance period start year					2011	2012	2013
Performance period end year					2013	2014	2015
Fair value of performance shares for grants awarded																900,000	800,000	700,000
Maximum Shares																						122,053	122,053
Common stock authorized, shares									400,000
Annual compensation withheld									10.00%
Annual compensation withheld, maximum limit									25,000
Employee contributions										100,000	100,000		100,000
Stock compensation expenses recognized										100,000	100,000	100,000
Number of restricted stock issued value																					138,000
RSU award vest each year																				33.00%
RSU expenses										$ 200,000