Segment Disclosures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2012 Segment	Mar. 31, 2011
Net Sales
Net sales	$ 607,088	$ 523,135
Segment Earnings
Segment Earnings	127,475	95,790
Corporate expense	(19,710)	(11,509)
Depreciation and amortization expense	(20,220)	(21,037)
Share-based compensation expense	(3,216)	(3,742)
Interest expense, net	(6,185)	(7,765)
Other (expense) income, net	(574)	(985)
Earnings from continuing operations before income taxes	77,570	50,752
Segment Disclosures (Textual) [Abstract]
Number of reportable segments	3
Electrical [Member]
Net Sales
Net sales	483,964	443,520
Segment Earnings
Segment Earnings	100,422	86,936
Steel Structures [Member]
Net Sales
Net sales	82,108	50,945
Segment Earnings
Segment Earnings	19,389	4,292
Hvac [Member]
Net Sales
Net sales	41,016	28,670
Segment Earnings
Segment Earnings	$ 7,664	$ 4,562

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Segment earnings.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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

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Amount of interest revenue net of interest expense for the reportable segment. Reporting interest revenue net of interest expense is permitted only when a majority of the segment's revenues are from interest and the chief operating decision maker relies primarily on net interest revenue to assess the performance of the segment and make decisions about resources to be allocated to the segment.

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The sum of expenses not otherwise specified in the taxonomy for managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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The net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items.

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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.

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