Goodwill and Identifiable Intangible Assets - Narrative (Details) (USD $)	3 Months Ended		12 Months Ended				3 Months Ended		12 Months Ended		3 Months Ended	12 Months Ended				12 Months Ended			12 Months Ended								6 Months Ended	12 Months Ended
	Dec. 31, 2010	Sep. 30, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Domestic Segments	Dec. 31, 2010 United States Facilities Services	Sep. 30, 2010 United States Facilities Services	Dec. 31, 2012 United States Facilities Services	Dec. 31, 2011 United States Facilities Services	Dec. 31, 2010 Domestic Construction	Dec. 31, 2012 Domestic Construction	Dec. 31, 2012 United States Mechanical Construction And Facilities Services	Dec. 31, 2011 United States Mechanical Construction And Facilities Services	Dec. 31, 2010 United States Mechanical Construction And Facilities Services	Dec. 31, 2012 United States Electrical Construction And Facilities Services	Dec. 31, 2011 United States Electrical Construction And Facilities Services	Dec. 31, 2010 United States Electrical Construction And Facilities Services	Dec. 31, 2012 Trade names (amortized)	Dec. 31, 2011 Trade names (amortized)	Dec. 31, 2012 Customer relationships	Dec. 31, 2011 Customer relationships	Dec. 31, 2011 Customer relationships United States Facilities Services	Dec. 31, 2012 Contract backlog	Dec. 31, 2012 Developed technology/Vendor network	Dec. 31, 2012 Non-competition agreements	Sep. 30, 2010 Trade names (amortized)	Dec. 31, 2011 Trade names (amortized)
Goodwill and Intangible Assets[Line Items]
Goodwill	$ 406,804,000		$ 566,588,000	$ 566,805,000	$ 406,804,000		$ 227,116,000		$ 361,615,000	$ 363,856,000			$ 201,150,000	$ 199,126,000	$ 175,865,000	$ 3,823,000	$ 3,823,000	$ 3,823,000
Goodwill acquired			2,000,000
Goodwill allocated									63.80%				35.50%			0.70%
Weighted average cost of capital used in annual testing for impairment							12.20%	12.50%	12.10%		13.20%	12.80%
Perpetual growth rate used for annual testing						2.70%	2.80%	2.80%			3.00%
Non-cash goodwill impairment charge	0	210,600,000	0	0	210,600,000
Impairment loss on identifiable intangible assets			0																								35,500,000	1,000,000
Non-cash impairment charge of finite-lived intangible assets			0	3,800,000	0															1,000,000		2,800,000	2,800,000
Contingent purchase price accrued and/or paid				1,900,000
Indefinite-lived intangible asset acquired			500,000
Intangible assets acquired				160,700,000
Amortization periods																			5 years 6 months		14 years			12 months	14 years	12 months
Amortization of identifiable intangible assets			$ 29,762,000	$ 26,350,000	$ 16,417,000