(7) Goodwill and Intangible Assets

There were no changes in goodwill for the six months ended June 30, 2016. Goodwill by operating segment is as follows (in thousands):

	Supply Chain Management		IT, Energy and Management Consulting		Aviation		Total
Balance as of December 31, 2015	$	63,113	$	30,883	$	104,549	$	198,545

Balance as of June 30, 2016	$	63,113	$	30,883	$	104,549	$	198,545

Intangible assets consist of the value of contract-related assets, acquired technologies and trade names. Amortization expense was approximately $4.0 million and $8.0 million for the three and six months ended June 30, 2016 and approximately $4.1 million and $7.7 million for the three and six months ended June 30, 2015, respectively.

Intangible assets were comprised of the following (in thousands):

	Cost		Accumulated Amortization			Accumulated Impairment Loss			Net Intangible Assets
June 30, 2016
Contract and customer-related	$	173,084	$	(53,211	)	$	(1,025	)	$	118,848
Acquired technologies		12,400		(5,715	)		-			6,685
Trade names – amortizable		16,730		(7,261	)		-			9,469
Total	$	202,214	$	(66,187	)	$	(1,025	)	$	135,002

December 31, 2015
Contract and customer-related	$	173,084	$	(46,611	)	$	(1,025	)	$	125,448
Acquired technologies		12,400		(5,151	)		-			7,249
Trade names – amortizable		16,730		(6,384	)		-			10,346
Total	$	202,214	$	(58,146	)	$	(1,025	)	$	143,043