Business Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 24, 2011	Sep. 25, 2010	Sep. 24, 2011 segment Y M	Sep. 25, 2010
Business Segments
Number of reportable segments			4
Sales	$ 702,352	$ 545,090	$ 1,990,373	$ 1,416,968
Intersegment Sales	30,160	17,259	81,623	40,176
Net Sales	672,192	527,831	1,908,750	1,376,792
Operating Income	72,033	47,143	185,953	116,094
Engineered Infrastructure Products segment:
Business Segments
Sales	222,243	197,601	597,590	467,959
Intersegment Sales	6,611	2,936	18,035	4,712
Net Sales	215,632	194,665	579,555	463,247
Operating Income	17,189	17,169	30,907	31,862
Engineered Infrastructure Products segment: \| Lighting and Traffic
Business Segments
Sales	157,273	139,387	420,122	344,873
Engineered Infrastructure Products segment: \| Access Systems
Business Segments
Sales	36,358	31,411	100,136	49,140
Engineered Infrastructure Products segment: \| Communication Structures
Business Segments
Sales	28,612	26,803	77,332	73,946
Utility Support Structures segment
Business Segments
Sales	159,815	122,241	422,022	350,307
Intersegment Sales	4,480	1,465	6,739	2,100
Net Sales	155,335	120,776	415,283	348,207
Operating Income	14,731	9,740	41,214	36,988
Utility Support Structures segment \| Steel
Business Segments
Sales	140,926	106,943	374,045	307,850
Utility Support Structures segment \| Concrete
Business Segments
Sales	18,889	15,298	47,977	42,457
Coatings segment
Business Segments
Sales	80,806	75,665	238,417	158,036
Intersegment Sales	11,852	9,204	34,283	21,721
Net Sales	68,954	66,161	204,134	136,315
Operating Income	14,238	13,577	39,600	27,993
Irrigation segment
Business Segments
Sales	150,618	88,255	485,367	309,053
Intersegment Sales		1	8	7
Net Sales	150,618	88,254	485,359	309,046
Operating Income	23,765	10,590	80,623	42,584
Other
Business Segments
Maximum percentage of sales of other businesses and activities to consolidated sales as basis for aggregation (as a percent)			10.00%
Sales	88,870	61,328	246,977	131,613
Intersegment Sales	7,217	3,653	22,558	11,636
Net Sales	81,653	57,975	224,419	119,977
Operating Income	12,607	7,124	32,901	20,096
Net corporate expense
Business Segments
Operating Income	$ (10,497)	$ (11,057)	$ (39,292)	$ (43,429)

The net result for the period of deducting operating expenses from operating revenues.

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Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 5

-Section 03

-Paragraph 1

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

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- Definition

Amount of revenue from transactions with other operating segments of the same entity.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 27

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

+ References

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

The maximum percentage of sales of individual business activities to total consolidated sales of operating segments that do not meet the quantitative thresholds and thus are not classified as reportable segments.

+ Details

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- Definition

Represents the number of reportable segments of the entity.

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