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Acquisitions (Details Textual) (USD $)
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3 Months Ended | 6 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 6 Months Ended | 6 Months Ended | 6 Months Ended | 6 Months Ended | |||||||||||
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Jun. 30, 2012
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Mar. 31, 2012
Entity
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Jun. 30, 2012
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Dec. 31, 2011
Entity
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Jun. 30, 2012
Electric Power Division [Member]
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Dec. 31, 2011
Electric Power Division [Member]
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Mar. 31, 2012
Electric Power Division [Member]
CANADA
Entity
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Dec. 31, 2011
Electric Power Division [Member]
CANADA
Entity
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Jun. 30, 2012
Electric Power Division [Member]
UNITED STATES
Entity
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Mar. 31, 2012
Electric Power Division [Member]
UNITED STATES
Entity
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Dec. 31, 2011
Electric Power Division [Member]
UNITED STATES
Entity
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Jun. 30, 2012
Natural Gas and Pipeline Division [Member]
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Dec. 31, 2011
Natural Gas and Pipeline Division [Member]
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Mar. 31, 2012
Natural Gas and Pipeline Division [Member]
UNITED STATES
Entity
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Dec. 31, 2011
Natural Gas and Pipeline Division [Member]
AUSTRALIA
Entity
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Dec. 31, 2011
Third and fourth quarters 2011 acquisitions [Member]
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Jun. 30, 2012
Phasor [Member]
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Mar. 02, 2012
Phasor [Member]
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Jun. 30, 2012
Crux [Member]
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Jan. 09, 2012
Crux [Member]
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Jun. 30, 2012
Microline [Member]
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Jan. 04, 2012
Microline [Member]
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Jun. 30, 2012
Service Electric [Member]
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Apr. 12, 2012
Service Electric [Member]
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| Acquisitions (Textual) [Abstract] | ||||||||||||||||||||||||
| Cash paid for acquisition | $ 80,800,000 | $ 2,900,000 | $ 27,500,000 | $ 6,800,000 | $ 20,300,000 | |||||||||||||||||||
| Number of shares issued for acquisition of company | 1,939,813 | 87,963 | 856,105 | 320,619 | 662,426 | |||||||||||||||||||
| Common stock value | 37,291,000 | 37,291,000 | 32,368,000 | 32,400,000 | 1,700,000 | 16,700,000 | 6,400,000 | 12,500,000 | ||||||||||||||||
| Payment of cash to repay acquiree debt | 3,400,000 | 4,200,000 | 900,000 | 5,900,000 | ||||||||||||||||||||
| Goodwill | 64,779,000 | 64,779,000 | 43,758,000 | 57,500,000 | 34,900,000 | 7,300,000 | 8,900,000 | |||||||||||||||||
| Number of business acquisitions completed | 3 | 5 | 1 | 3 | 1 | 1 | 1 | 1 | 1 | |||||||||||||||
| Acquisitions (Additional Textual) [Abstract] | ||||||||||||||||||||||||
| Accounts receivables with fair value | 15,300,000 | 15,300,000 | 16,100,000 | |||||||||||||||||||||
| Goodwill expected to be deductible for income tax | 52,900,000 | 52,900,000 | 13,100,000 | |||||||||||||||||||||
| Revenues contributed by acquisitions | 19,600,000 | 24,700,000 | ||||||||||||||||||||||
| Income before income taxes contributed by acquisitions | $ 700,000 | $ 600,000 | ||||||||||||||||||||||