Goodwill and Intangible Assets

Identifiable intangible assets that are separable and have determinable useful lives are valued separately and amortized over their benefit period. The following is the gross carrying value and accumulated amortization of the Company’s identifiable intangible assets as of December 31, 2018 and December 31, 2017 (in thousands):



	December 31, 2018							December 31, 2017
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Tradenames	$	15,980	$	(10,423	)	$	5,557	$	15,980	$	(7,283	)	$	8,697
Customer relationships	250,498		(112,757		)	137,741		225,488		(72,349		)	153,139
Other intangible assets	3,489		(911		)	2,578		3,462		(762		)	2,700
	$	269,967	$	(124,091	)	$	145,876	$	244,930	$	(80,394	)	$	164,536

The weighted average amortization period of these intangible assets in the aggregate is 3.9 years. Total amortization expense of intangible assets above was $44.0 million and $41.5 million for the years ended December 31, 2018 and 2017, respectively.

Future amortization for the next five years and thereafter is as follows (in thousands):



Years Ending December 31,
2019	$	45,871
2020	44,709
2021	27,074
2022	11,930
2023	5,547
Thereafter	10,745
	$	145,876

Changes in goodwill between December 31, 2017 and December 31, 2018, consisted of the following (in thousands):



	Carrying Value
Balance at December 31, 2017	$	452,728
Goodwill acquired	34,314
Purchase price allocation adjustments from prior periods	64
Impact of foreign currency exchange rates	(2,165		)
Balance at December 31, 2018	$	484,941

Changes to initial purchase price allocations related to acquisitions may arise from changes in estimates from conditions that existed at the applicable acquisition date and as a result of net working capital adjustments. The Company performed its goodwill impairment test as of October 1, 2018, and the fair value substantially exceeded the carrying value, as such, there was no impairment related to goodwill.