Earning Per Share Data - Basic and Diluted Earnings Per Share (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 3,764,000	$ 3,415,000	$ 6,110,000	$ 4,809,000
Common Shares:
Weighted average common shares outstanding	14,482,000	14,390,000	14,470,000	14,384,000
Effect of dilutive stock options	246,000	207,000	255,000	210,000
Diluted shares outstanding	14,728,000	14,597,000	14,725,000	14,594,000
Basic:
Net earnings per share	$ 0.26	$ 0.24	$ 0.42	$ 0.33
Diluted:
Net earnings per share	$ 0.26	$ 0.23	$ 0.41	$ 0.33