Industry Segment Information (Schedule Of Segment Reporting Information, By Segment) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013
Segment Reporting Information [Line Items]
Total operating revenues	$ 152,804	$ 175,539	$ 300,475	$ 322,909
Segment operating income	24,554	33,201	45,373	59,351
Unallocated general and administrative expenses	(3,641)	(3,755)	(8,468)	(7,641)
Interest and other income (expense), net	(124)	42	(299)	161
Earnings before income taxes	20,789	29,488	36,606	51,871
Capital Expenditures	2,966	3,127	5,353	5,342
Depreciation and Amortization	3,677	3,110	7,384	6,240
Irrigation [Member]
Segment Reporting Information [Line Items]
Number of operating segments			13
Total operating revenues	135,884	162,677	265,067	296,894
Segment operating income	24,548	35,267	44,859	62,735
Capital Expenditures	2,709	2,965	4,937	5,051
Depreciation and Amortization	2,341	1,692	4,699	3,396
Infrastructure [Member]
Segment Reporting Information [Line Items]
Number of operating segments			2
Total operating revenues	16,920	12,862	35,408	26,015
Segment operating income	6	(2,066)	514	(3,384)
Capital Expenditures	257	162	416	291
Depreciation and Amortization	$ 1,336	$ 1,418	$ 2,685	$ 2,844

Segment operating income (loss)

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- Definition

Unallocated general and administrative expenses

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- Definition

Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(1)(i))

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The amount of interest income and other income recognized during the period. Included in this element is interest derived from investments in debt securities, cash and cash equivalents, and other investments which reflect the time value of money or transactions in which the payments are for the use or forbearance of money and other income from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business).

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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The other noncash expense, not otherwise specified in the taxonomy, charged against earnings in the period to allocate the cost of tangible and intangible assets over their remaining economic lives.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (a)

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-Topic 230

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-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.3)

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The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

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-Section 45

-Paragraph 13

-Subparagraph (c)

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

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