Industry Segment Information (Schedule of Segment Reporting Information Impacts on Statement of Operations, by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2019	May 31, 2018	May 31, 2019	May 31, 2018
Segment Reporting Information [Line Items]
Total operating revenues	$ 121,054	$ 169,571	$ 342,187	$ 424,436
Total operating income	4,475	18,814	2,055	32,306
Interest and other expense, net	(1,246)	(1,369)	(2,213)	(4,393)
Earnings (loss) before income taxes	3,229	17,445	(158)	27,913
Capital expenditures	8,509	2,205	20,210	6,920
Depreciation and amortization	3,563	4,252	10,452	12,851
Irrigation [Member]
Segment Reporting Information [Line Items]
Total operating revenues	98,618	128,421	281,994	343,639
Total operating income	11,037	11,718	26,341	31,502
Capital expenditures	3,828	1,950	8,306	5,985
Depreciation and amortization	2,373	2,974	7,071	9,047
Irrigation [Member] | North America [Member]
Segment Reporting Information [Line Items]
Total operating revenues	62,974	87,407	177,118	234,023
Irrigation [Member] | International [Member]
Segment Reporting Information [Line Items]
Total operating revenues	35,644	41,015	104,876	109,617
Infrastructure [Member]
Segment Reporting Information [Line Items]
Total operating revenues	22,436	41,150	60,193	80,797
Total operating income	3,537	14,248	7,259	20,058
Capital expenditures	3,064	252	3,430	716
Depreciation and amortization	905	1,153	2,789	3,435
Corporate Segment
Segment Reporting Information [Line Items]
Total operating income	(10,099)	(7,152)	(31,545)	(19,254)
Capital expenditures	1,617	3	8,474	219
Depreciation and amortization	$ 285	$ 125	$ 592	$ 369