Goodwill and Identifiable Assets (Tables)

6 Months Ended

Jun. 30, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

The changes in the carrying amount of goodwill for six months ended June 30, 2017 and the year ended December 31, 2016 were as follows (in thousands):



	Apex Segment		Oxford Segment			Total
Balance as of December 31, 2015	$	644,617	$	230,289		$	874,906
Translation adjustment	—		(1,393		)	(1,393		)
Balance as of December 31, 2016	644,617		228,896			873,513
Translation adjustment	—		1,918			1,918
Balance as of June 30, 2017	$	644,617	$	230,814		$	875,431

Schedule of Acquired Intangible Assets

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



		As of June 30, 2017						As of December 31, 2016
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Subject to amortization:
Customer relationships	2 - 10 years	$	196,827	$	108,872	$	87,955	$	196,204	$	98,804	$	97,400
Contractor relationships	2 - 5 years	69,820		55,191		14,629		69,721		50,528		19,193
Non-compete agreements	2 - 7 years	10,892		5,712		5,180		10,861		4,922		5,939
In-use software	6 years	18,900		11,241		7,659		18,900		9,666		9,234
Favorable contracts	5 years	900		563		337		900		453		447
		297,339		181,579		115,760		296,586		164,373		132,213
Not subject to amortization:
Trademarks		245,780		—		245,780		245,517		—		245,517
Total		$	543,119	$	181,579	$	361,540	$	542,103	$	164,373	$	377,730

Schedule of Estimated Future Amortization Expense

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



Remainder of 2017	$	16,110
2018	28,892
2019	22,003
2020	14,498
2021	11,816
Thereafter	22,441
	$	115,760