Quarterly report pursuant to Section 13 or 15(d)

Acquisitions (Details Textual)

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Acquisitions (Details Textual) (USD $)
 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended 3 Months Ended 3 Months Ended
Mar. 31, 2012
Entity
Dec. 31, 2011
Entity
Mar. 31, 2012
Electric Power Division [Member]
Dec. 31, 2011
Electric Power Division [Member]
Mar. 31, 2012
Electric Power Division [Member]
CANADA
Entity
Dec. 31, 2011
Electric Power Division [Member]
CANADA
Entity
Mar. 31, 2012
Electric Power Division [Member]
UNITED STATES
Entity
Dec. 31, 2011
Electric Power Division [Member]
UNITED STATES
Entity
Mar. 31, 2012
Natural Gas and Pipeline Division [Member]
Dec. 31, 2011
Natural Gas and Pipeline Division [Member]
Mar. 31, 2012
Natural Gas and Pipeline Division [Member]
UNITED STATES
Entity
Dec. 31, 2011
Natural Gas and Pipeline Division [Member]
AUSTRALIA
Entity
Mar. 31, 2012
Third and fourth quarters 2011 acquisitions [Member]
Mar. 31, 2012
Phasor [Member]
Mar. 02, 2012
Phasor [Member]
Mar. 31, 2012
Crux [Member]
Jan. 09, 2012
Crux [Member]
Mar. 31, 2012
Microline [Member]
Jan. 04, 2012
Microline [Member]
Acquisitions (Textual) [Abstract]                                      
Cash paid for acquisition                         $ 80,800,000   $ 2,900,000   $ 27,500,000   $ 6,800,000
Number of shares issued for acquisition of company                         1,939,813 87,963   856,105   320,619  
Common stock value 24,783,000 32,368,000                     32,400,000   1,700,000   16,700,000   6,400,000
Payment of cash to repay acquiree debt                         3,400,000       4,200,000   900,000
Accounts receivables with fair value 8,400,000 16,100,000                                  
Goodwill 42,296,000 43,758,000 35,000,000 34,900,000         7,300,000 8,900,000                  
Number of business acquisitions completed 3 5     1 3 1 1     1 1              
Acquisitions (Additional Textual) [Abstract]                                      
Goodwill expected to be deductible for income tax 38,800,000 13,100,000                                  
Revenues contributed by acquisitions 13,900,000                                    
Income before income taxes contributed by acquisitions $ 3,100,000