Industry Segment Information (Schedule of Segment Reporting Information, by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017
Segment Reporting Information [Line Items]
Total operating revenues	$ 101,885	$ 121,054	$ 109,182	$ 111,951	$ 123,269	$ 169,571	$ 130,339	$ 124,526	$ 444,072	$ 547,705	$ 517,985
Total operating income									6,115	39,012	40,649
Interest and other expense, net									(4,008)	(5,159)	(4,934)
Earnings before income taxes									2,107	33,853	35,715
Capital expenditures									23,211	11,054	8,863
Depreciation and amortization									14,018	16,514	16,678
Total Assets	500,314				499,815				500,314	499,815	506,032
Irrigation [Member]
Segment Reporting Information [Line Items]
Total operating revenues									351,498	439,858	418,041
Total operating income									29,804	41,933	42,774
Capital expenditures									9,473	9,259	6,313
Depreciation and amortization									9,500	11,412	11,840
Total Assets	292,202				277,712				292,202	277,712	337,446
Irrigation [Member] | North America [Member]
Segment Reporting Information [Line Items]
Total operating revenues									218,627	294,617	340,660
Irrigation [Member] | International [Member]
Segment Reporting Information [Line Items]
Total operating revenues									132,871	145,241	77,381
Infrastructure [Member]
Segment Reporting Information [Line Items]
Total operating revenues									92,574	107,847	99,944
Total operating income									16,599	23,857	20,131
Capital expenditures									4,928	938	1,562
Depreciation and amortization									3,663	4,611	4,452
Total Assets	85,848				69,919				85,848	69,919	80,187
Corporate Segment
Segment Reporting Information [Line Items]
Total operating income									(40,288)	(26,778)	(22,256)
Capital expenditures									8,810	857	988
Depreciation and amortization									855	491	386
Total Assets	$ 122,264				$ 152,184				$ 122,264	$ 152,184	$ 88,399