Segment Data and Foreign Operations (Details) $ in Thousands	3 Months Ended						6 Months Ended			9 Months Ended
	Feb. 29, 2020 USD ($) segment	Nov. 30, 2019 USD ($)	Aug. 31, 2019 USD ($) segment	Feb. 28, 2019 USD ($)	Nov. 30, 2018 USD ($)	Aug. 31, 2018 USD ($)	Feb. 29, 2020 USD ($) segment	Aug. 31, 2019 USD ($)	Feb. 28, 2019 USD ($)	Aug. 31, 2019 USD ($)
Segment data
Number of operating segments | segment	3		2				3
Revenue	$ 65,582			$ 66,631			$ 132,384		$ 139,134
Income before income taxes	10,805			6,932			20,876		18,740
Interest	56			162			111		366
Depreciation							2,041		2,491
Amortization							5,826		6,225
Exit costs related to facilities	60						709		260
Impairment of goodwill				2,410					2,410
Curtailment and settlement loss				273					473
Total assets	326,269		$ 307,968				326,269	$ 307,968		$ 307,968
Granite Falls Location
Segment data
Exit costs related to facilities	60						559	526
Pawtucket, RI manufacturing facility
Segment data
Exit costs related to facilities					$ 260	$ 1,272	0		0	0
Adhesives, Sealants and Additives
Segment data
Revenue	24,440			26,107			50,262		52,805
Income before income taxes	6,750			4,756			14,232		13,021
Interest	21			59			42		138
Depreciation	278			382			592		765
Amortization	2,356			2,339			4,693		4,679
Impairment of goodwill				2,410
Total assets	139,992		135,583				139,992	135,583		135,583
Industrial Tapes
Segment data
Revenue	30,055			31,158			60,179		64,620
Income before income taxes	8,402			7,513			15,039		14,051
Interest	29			71			54		155
Depreciation	418			438			819		894
Amortization	450			450			900		900
Total assets	70,600		77,085				70,600	77,085		77,085
Corrosion Protection and Waterproofing
Segment data
Revenue	11,087			9,366			21,943		21,709
Income before income taxes	4,127			2,384			8,091		6,850
Interest	6			32			15		73
Depreciation	151			164			305		339
Amortization	106			323			233		646
Total assets	32,537		32,478				32,537	32,478		32,478
Industrial Materials | Pawtucket, RI manufacturing facility
Segment data
Exit costs related to facilities									260
Reportable segments
Segment data
Income before income taxes	19,279			14,653			37,362		33,922
Total assets	243,129		245,146				243,129	245,146		245,146
Corporate and common costs
Segment data
Income before income taxes	(8,474)			(7,721)			(16,486)		(15,182)
Curtailment and settlement loss				$ 273					$ 473
Total assets	83,140		$ 62,822				83,140	$ 62,822		$ 62,822
Engineering Studies related to Facility Consolidation and Rationalization Initiative
Segment data
Business development cost	$ 0	$ 150					$ 150