Earnings per Share Data - Basic and Diluted Earnings Per Share (Detail) - USD ($)	3 Months Ended									9 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019		Mar. 31, 2019	[1]	Dec. 31, 2018	[1]	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Income	$ 4,322,000	$ (655,000)	$ 2,489,000	$ 2,444,000	[1]	$ 7,460,000		$ 313,000		$ 6,156,000	$ 10,217,000
Common Shares:
Weighted average common shares outstanding	14,601,000			14,541,000						14,592,000	14,541,000
Effect of dilutive stock options	118,000			164,000						125,000	163,000
Diluted shares outstanding	14,719,000			14,705,000						14,717,000	14,704,000
Basic:
Net earnings per share	$ 0.30			$ 0.17						$ 0.42	$ 0.70
Diluted:
Net earnings per share	$ 0.29			$ 0.17						$ 0.42	$ 0.69

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