General - Fair Value of Identified Assets and Liabilities (Details) - USD ($) $ in Thousands		3 Months Ended
	Mar. 01, 2015	Mar. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill at March 31, 2016		$ 294,479	$ 249,120
Underground Solutions
Business Acquisition [Line Items]
Cash		3,630
Receivables and cost and estimated earnings in excess of billings		6,373
Inventories		12,839
Prepaid expenses and other current assets		777
Property, plant and equipment		2,755
Identified intangible assets		34,400
Deferred income tax assets		12,212
Other assets		29
Accounts payable		(4,653)
Accrued expenses		(5,011)
Billings in excess of cost and estimated earnings		(2,943)
Deferred income tax liabilities		(15,232)
Total identifiable net assets		45,176
Total consideration recorded		88,797
Less: total identifiable net assets		45,176
Goodwill at March 31, 2016		43,621
Schultz Mechanical Contractors, Inc.
Business Acquisition [Line Items]
Cash		0
Receivables and cost and estimated earnings in excess of billings		1,086
Inventories		0
Prepaid expenses and other current assets		19
Property, plant and equipment		162
Identified intangible assets		3,060
Deferred income tax assets		0
Other assets		0
Accounts payable		(663)
Accrued expenses		0
Billings in excess of cost and estimated earnings		0
Deferred income tax liabilities		0
Total identifiable net assets		3,664
Total consideration recorded	$ 7,700	7,662
Less: total identifiable net assets		3,664
Goodwill at March 31, 2016		$ 3,998