Goodwill and Identifiable Assets (Tables)

6 Months Ended

Jun. 30, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

The changes in the carrying amount of goodwill for the six months ended June 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	—		—			526,565		526,565
Translation adjustment	—		(648		)	—		(648		)
Balance as of June 30, 2018	$	662,084	$	231,363		$	526,565	$	1,420,012

Schedule of Acquired Intangible Assets

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



		June 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	$	343,762	$	129,680	$	214,082	$	202,588	$	119,272	$	83,316
Contractor relationships	2 - 5 years	71,130		63,123		8,007		71,121		59,174		11,947
Backlog	1 year	26,100		8,700		17,400		—		—		—
Non-compete agreements	2 - 7 years	22,236		7,972		14,264		11,850		6,600		5,250
In-use software	6 years	18,900		14,391		4,509		18,900		12,816		6,084
Favorable contracts	5 years	1,400		755		645		900		673		227
		483,528		224,621		258,907		305,359		198,535		106,824
Not subject to amortization:
Trademarks		262,291		—		262,291		245,942		—		245,942
Total		$	745,819	$	224,621	$	521,198	$	551,301	$	198,535	$	352,766

Schedule of Estimated Future Amortization Expense

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



Remainder of 2018	$	37,100
2019	51,310
2020	40,298
2021	35,482
2022	24,445
Thereafter	70,272
	$	258,907