Earnings per Share Data - Basic and Diluted Earnings Per Share (Detail) - USD ($)	3 Months Ended						6 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019		Dec. 31, 2018	[1]	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net Income (Loss)	$ (655,000)	$ 2,489,000	$ 7,460,000	[1]	$ 313,000		$ 1,834,000	$ 7,773,000
Common Shares:
Weighted average common shares outstanding	14,586,000		14,541,000				14,586,000	14,541,000
Effect of dilutive stock options			167,000				128,000	164,000
Diluted shares outstanding	14,586,000		14,708,000				14,714,000	14,705,000
Basic:
Net earnings (loss) per share	$ (0.04)		$ 0.51				$ 0.13	$ 0.53
Diluted:
Net earnings (loss) per share	$ (0.04)		$ 0.51				$ 0.12	$ 0.53

[1] The balances as of September 30, 2018, December 31, 2018 and March 31, 2019, and the amounts for the quarter and six months ended March 31, 2019, have been adjusted to reflect the change in inventory accounting method, as described in Note 3 to the Condensed Consolidated Financial Statements.