Goodwill and Identifiable 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 for the years ended December 31, 2017 and 2016 are as follows (in thousands):

	Apex		Oxford			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
Stratacuity acquisition	17,467		—			17,467
Translation adjustment			3,115			3,115
Balance as of December 31, 2017	$	662,084	$	232,011		$	894,095

Schedule of Acquired Intangible Assets

As of December 31, 2017 and 2016, the Company had the following acquired intangible assets (in thousands):

		2017						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	$	202,588	$	119,272	$	83,316	$	196,204	$	98,804	$	97,400
Contractor relationships	2 - 5 years	71,121		59,174		11,947		69,721		50,528		19,193
Non-compete agreements	2 - 7 years	11,850		6,600		5,250		10,861		4,922		5,939
In-use software	6 years	18,900		12,816		6,084		18,900		9,666		9,234
Favorable contracts	5 years	900		673		227		900		453		447
		305,359		198,535		106,824		296,586		164,373		132,213
Not subject to amortization:
Trademarks		245,942		—		245,942		245,517		—		245,517
Total		$	551,301	$	198,535	$	352,766	$	542,103	$	164,373	$	377,730

Schedule of Estimated Future Amortization Expense

Estimated amortization for each of the next five years and thereafter follows (in thousands):

2018	$	30,322
2019	23,287
2020	15,613
2021	12,753
2022	8,044
Thereafter	16,805
	$	106,824