Total expenditures for additions to long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets of the reportable segment; if the amount: (a) is included in the determination of segment assets reviewed by the chief operating decision maker or (b) is otherwise regularly provided to the chief operating decision maker, even if not included in the determination of segment assets.

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Industry Segment Information (Schedule Of Segment Reporting Information, By Segment) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2013	Aug. 31, 2012	Aug. 31, 2011
Segment Reporting Information [Line Items]
Total operating revenues	$ 148,397	$ 219,542	$ 175,539	$ 147,370	$ 127,817	$ 172,099	$ 132,134	$ 119,205	$ 690,848	$ 551,255	$ 478,890
Operating Income (Loss)									107,061	65,510	56,586
Unallocated general and administrative expenses									(43,441)	(38,198)	(33,659)
Interest and other income (expense), net									246	(402)	(72)
Total	15,686	39,750	29,488	22,383	12,653	28,587	19,427	4,441	107,307	65,108	56,514
Capital Expenditures									11,136	9,890	8,405
Depreciation and amortization									12,600	12,468	11,734
Assets	512,296				415,531				512,296	415,531	381,144
Irrigation [Member]
Segment Reporting Information [Line Items]
Total operating revenues									625,996	475,299	369,930
Capital Expenditures									10,687	7,942	5,490
Depreciation and amortization									7,147	6,959	6,009
Assets	391,527				303,741				391,527	303,741	267,275
Infrastructure [Member]
Segment Reporting Information [Line Items]
Total operating revenues									64,852	75,956	108,960
Capital Expenditures									449	1,948	2,915
Depreciation and amortization									5,453	5,509	5,725
Assets	120,769				111,790				120,769	111,790	113,869
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)									124,584	80,248	71,604
Operating Segments [Member] \| Irrigation [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)									125,395	80,259	59,703
Operating Segments [Member] \| Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)									(811)	(11)	11,901
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Unallocated general and administrative expenses									$ (17,523)	$ (14,738)	$ (15,018)