Quarterly report pursuant to Section 13 or 15(d)

Subsequent Events - Additional Information (Detail)

v3.2.0.727
Subsequent Events - Additional Information (Detail)
$ in Millions
3 Months Ended 6 Months Ended 12 Months Ended
Sep. 30, 2015
USD ($)
Entity
Jun. 30, 2015
Entity
Mar. 31, 2015
Entity
Jun. 30, 2015
USD ($)
Entity
Dec. 31, 2014
USD ($)
Entity
Subsequent Event [Line Items]          
Number of business acquisitions   3 3 6 9
Cash paid for acquisitions | $       $ 64.7 $ 279.5
Aggregate consideration paid or payable, Common stock value | $         $ 134.5
Electric Power Infrastructure Services Business [Member]          
Subsequent Event [Line Items]          
Number of business acquisitions       4  
United States [Member] | Electric Power Infrastructure Services Business [Member]          
Subsequent Event [Line Items]          
Number of business acquisitions   2   2 1
Australia [Member] | Electric Power Infrastructure Services Business [Member]          
Subsequent Event [Line Items]          
Number of business acquisitions         1
Scenario Forecast [Member]          
Subsequent Event [Line Items]          
Cash paid for acquisitions | $ $ 28.8        
Aggregate consideration paid or payable, Common stock value | $ $ 7.7        
Scenario Forecast [Member] | United States [Member] | Electric Power Infrastructure Services Business [Member]          
Subsequent Event [Line Items]          
Number of business acquisitions 2        
Scenario Forecast [Member] | Australia [Member] | Electric Power Infrastructure Services Business [Member]          
Subsequent Event [Line Items]          
Number of business acquisitions 1