Goodwill and Identifiable Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

The changes in the carrying amount of goodwill by reportable segments during the years ended December 31, 2017 and 2016 were as follows (in thousands):

	United States electrical construction and facilities services segment		United States mechanical construction and facilities services segment			United States building services segment		United States industrial services segment			Total
Balance at December 31, 2015	$	3,823	$	226,071		$	228,637	$	384,639		$	843,170
Acquisitions, sales and purchase price adjustments	119,777		525			16,156		—			136,458
Balance at December 31, 2016	123,600		226,596			244,793		384,639			979,628
Acquisitions, sales and purchase price adjustments	2,107		30,969			9,640		—			42,716
Transfers	—		(1,300		)	1,300		—			—
Impairment	—		—			—		(57,451		)	(57,451		)
Balance at December 31, 2017	$	125,707	$	256,265		$	255,733	$	327,188		$	964,893

Schedule of Intangible Assets

Identifiable intangible assets as of December 31, 2017 and 2016 consist of the following (in thousands):

	December 31, 2017
	Gross Carrying Amount		Accumulated Amortization			Accumulated Impairment Charge			Total
Contract backlog	$	55,545	$	(55,229	)	$	—		$	316
Developed technology/Vendor network	95,661		(50,479		)	—			45,182
Customer relationships	500,756		(206,319		)	(4,834		)	289,603
Non-competition agreements	10,220		(10,178		)	—			42
Trade names (amortized)	32,848		(19,461		)	—			13,387
Trade names (unamortized)	198,739		—			(52,233		)	146,506
Total	$	893,769	$	(341,666	)	$	(57,067	)	$	495,036

	December 31, 2016
	Gross Carrying Amount		Accumulated Amortization			Accumulated Impairment Charge			Total
Contract backlog	$	48,645	$	(48,412	)	$	—		$	233
Developed technology/Vendor network	95,661		(45,616		)	—			50,045
Customer relationships	466,556		(173,156		)	(4,834		)	288,566
Non-competition agreements	10,220		(10,041		)	—			179
Trade names (amortized)	32,848		(15,847		)	—			17,001
Trade names (unamortized)	183,239		—			(51,865		)	131,374
Total	$	837,169	$	(293,072	)	$	(56,699	)	$	487,398

Schedule of Estimated Future Amortization Expense

The following table presents the estimated future amortization expense of identifiable intangible assets in the following years (in thousands):

2018	$	40,579
2019	38,281
2020	38,100
2021	37,306
2022	35,103
Thereafter	159,161
	$	348,530