Goodwill and Identified Intangible Assets Goodwill and Identified Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Finite-Lived Intangible Assets [Line Items]
Additions to goodwill through acquisitions				$ 3,998
Amortization of Intangible Assets	$ 3,200		$ 3,600	$ 6,400	$ 7,000
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