Reconciliation of Basic and Diluted Earnings Per Share Attributable to Common Stock (Detail) (USD $)	3 Months Ended			9 Months Ended
	Jun. 30, 2013	Jun. 30, 2012		Jun. 30, 2013	Jun. 30, 2012
Income Per Common Share [Line Items]
Net income	$ 4,063,000	$ 1,141,000	[1]	$ 13,270,000	$ 9,961,000	[1]
Income allocable to unvested restricted stock	(93,000)	(12,000)	[1]	(305,000)	(102,000)	[1]
Basic income attributable to common stock	3,970,000	1,129,000	[1]	12,965,000	9,859,000	[1]
Reallocation of participating earnings	1,000			2,000	1,000	[1]
Diluted income attributable to common stock	$ 3,971,000	$ 1,129,000	[1]	$ 12,967,000	$ 9,860,000	[1]
Weighted average common shares outstanding:
Basic:	7,873,698	7,846,417	[1]	7,861,425	7,839,983	[1]
Dilutive common stock options	48,858	26,006	[1]	38,701	41,204	[1]
Diluted:	7,922,556	7,872,423	[1]	7,900,126	7,881,187	[1]
Basic income attributable to a share of common stock	$ 0.50	$ 0.14	[1]	$ 1.65	$ 1.26	[1]
Diluted income attributable to a share of common stock	$ 0.50	$ 0.14	[1]	$ 1.64	$ 1.25	[1]

[1] Prior year earnings per share calculations have been adjusted for the two-class method to reflect restricted shares that were not reflected as participating in prior periods. Basic earnings per share as previously reported for the quarter and nine months ended June 30, 2012 was $0.15 and $1.27, respectively. Diluted earnings per share as previously reported for the quarter and nine months ended June 30, 2012 was $0.14 and $1.26, respectively. Basic weighted average shares outstanding as previously reported for the quarter and nine months ended June 30, 2012 were 7,846,417 and 7,839,983, respectively. Diluted weighted average shares outstanding as previously reported for the quarter and nine months ended June 30, 2012 were 7,924,009 and 7,934,367, respectively. The impact on all prior period financial statements is deemed immaterial.