Goodwill and Identified Intangible Assets Goodwill and Identified Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Finite-Lived Intangible Assets [Line Items]
Additions to goodwill through acquisitions				$ 3,998
Amortization of Intangible Assets	$ 3,500		$ 3,600	$ 9,900	$ 10,600
Schultz Mechanical Contractors, Inc. [Member]
Finite-Lived Intangible Assets [Line Items]
Additions to goodwill through acquisitions	$ 400	$ 3,600
Schultz Mechanical Contractors, Inc. [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets acquired through acquisition		2,300
Schultz Mechanical Contractors, Inc. [Member] | Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets acquired through acquisition		700
Schultz Mechanical Contractors, Inc. [Member] | Non-competes [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets acquired through acquisition		$ 100