Summary of Significant Accounting Policies - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Unbilled revenues for unapproved change orders	$ 18,800,000	$ 19,200,000
Claims on uncompleted contracts	3,000,000	400,000
Accounts receivable, unapproved contract claims	2,300,000	2,900,000
Accouts receivable, contractually billed amounts on contracts related to unapproved contract claims	54,000,000	56,100,000
Accounts receivable, retainage	177,800,000	189,700,000
Accounts receivable, retainage estimated to be collected in next fiscal year	87.00%
Accounts payable, retainage	35,700,000	47,000,000
Accounts payable, retainage estimated to be paid in next fiscal year	95.00%
Accounts receivable, net	1,234,187,000	1,268,226,000
Allowance for doubtful accounts	10,424,000	11,890,000
Provision for doubtful accounts	2,918,000	3,533,000	1,163,000
Non-cash expense for impairment of property, plant and equipment	0	0	0
Insurance liabilities, current	28,800,000	29,200,000
Insurance liabilities, noncurrent	106,300,000	112,800,000
Buildings
Property, Plant and Equipment [Line Items]
Estimated useful life	25 years
Machinery and Equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Machinery and Equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Vehicles, Furniture and Fixtures, and Computer Hardware and Software | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Vehicles, Furniture and Fixtures, and Computer Hardware and Software | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
United States Mechanical Construction And Facilities Services
Property, Plant and Equipment [Line Items]
Loss on contracts		$ 24,500,000