Industry Segment Information (Schedule Of Segment Reporting Information, By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Nov. 30, 2016	Nov. 30, 2015	Aug. 31, 2016
Segment Reporting Information [Line Items]
Total operating revenues	$ 110,390	$ 121,622
Segment operating income	2,735	11,748
Unallocated general and administrative expenses	(11,355)	(9,015)
Earnings before income taxes	1,335	10,396
Capital expenditures	1,390	4,705
Depreciation and amortization	4,035	4,295
Assets	480,943	511,269	$ 487,515
Irrigation [Member]
Segment Reporting Information [Line Items]
Capital expenditures	950	3,152
Depreciation and amortization	2,823	2,953
Assets	340,711	335,920	341,972
Infrastructure [Member]
Segment Reporting Information [Line Items]
Capital expenditures	440	1,553
Depreciation and amortization	1,109	1,201
Assets	80,002	78,551	83,531
Corporate [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	103	141
Assets	60,230	96,798	$ 62,012
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating revenues	110,390	121,622
Segment operating income	8,124	15,774
Operating Segments [Member] | Irrigation [Member]
Segment Reporting Information [Line Items]
Total operating revenues	89,852	101,327
Segment operating income	5,150	12,692
Operating Segments [Member] | Infrastructure [Member]
Segment Reporting Information [Line Items]
Total operating revenues	20,538	20,295
Segment operating income	2,974	3,082
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Unallocated general and administrative expenses	(5,389)	(4,026)
Interest and other expense, net	(1,400)	(1,352)
Earnings before income taxes	$ 1,335	$ 10,396