Goodwill and Identifiable Assets (Tables)

9 Months Ended

Sep. 30, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

The changes in the carrying amount of goodwill for the nine months ended September 30, 2018 and the year ended December 31, 2017 were as follows (in thousands):



	Apex Segment		Oxford Segment			ECS Segment		Total
Balance as of December 31, 2016	$	644,617	$	228,896		$	—	$	873,513
Stratacuity acquisition	17,467		—			—		17,467
Translation adjustment	—		3,115			—		3,115
Balance as of December 31, 2017	662,084		232,011			—		894,095
ECS acquisition	—		—			527,388		527,388
Translation adjustment	—		(847		)	—		(847		)
Balance as of September 30, 2018	$	662,084	$	231,164		$	527,388	$	1,420,636

Schedule of Acquired Intangible Assets

Acquired intangible assets consisted of the following (in thousands):



		September 30, 2018						December 31, 2017
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Subject to amortization:
Customer and contractual relationships	2 - 13 years	$	343,707	$	135,739	$	207,968	$	202,588	$	119,272	$	83,316
Contractor relationships	2 - 5 years	71,121		65,102		6,019		71,121		59,174		11,947
Backlog	1 year	26,100		17,400		8,700		—		—		—
Non-compete agreements	2 - 7 years	22,234		8,950		13,284		11,850		6,600		5,250
In-use software	6 years	18,900		15,178		3,722		18,900		12,816		6,084
Favorable contracts	5 years	1,400		804		596		900		673		227
		483,462		243,173		240,289		305,359		198,535		106,824
Not subject to amortization:
Trademarks		262,268		—		262,268		245,942		—		245,942
Total		$	745,730	$	243,173	$	502,557	$	551,301	$	198,535	$	352,766

Schedule of Estimated Future Amortization Expense

Estimated future amortization expense is as follows (in thousands):



Remainder of 2018	$	18,545
2019	51,296
2020	40,287
2021	35,469
2022	24,437
Thereafter	70,255
	$	240,289