Note 9—Goodwill and Intangible Assets

During the years ended December 31, 2017 and 2016, the change in the carrying amount of goodwill was as follows (in thousands):



Balance at January 1, 2016	$	41,327
Acquisition of Wyoming Refining (1)	64,994
Mid Pac acquisition purchase price allocation adjustment (2)	(589		)
Balance at December 31, 2016	105,732
Wyoming Refining acquisition purchase price allocation adjustment (1)	1,455
Balance at December 31, 2017	$	107,187

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(1)	Please read Note 4—Acquisitions for further discussion.


(2)	During 2016, the purchase price allocation was adjusted to record an increase to tax receivables and a decrease to goodwill of $0.6 million. The tax receivable was recorded in connection with a tax refund received by Mid Pac in the first quarter of 2016.

Intangible assets consist of the following (in thousands):



	December 31,
	2017			2016
Intangible assets:
Railcar leases	$	3,249		$	3,249
Trade names and trademarks	6,267			6,267
Customer relationships	32,064			32,064
Total intangible assets	41,580			41,580
Accumulated amortization:
Railcar leases	(3,249		)	(2,599		)
Trade name and trademarks	(4,951		)	(4,864		)
Customer relationships	(6,776		)	(4,205		)
Total accumulated amortization	(14,976		)	(11,668		)
Net:
Railcar leases	—			650
Trade name and trademarks	1,316			1,403
Customer relationships	25,288			27,859
Total intangible assets, net	$	26,604		$	29,912

At September 30, 2015, we conducted an impairment test related to goodwill and intangible assets in our Texadian reporting unit. As of result of canceling the charter on the barges used to transport crude from Canada to the U.S. Gulf Coast in the Texadian business and negative cash flows, we concluded that goodwill and the supplier relationships intangible asset were fully impaired at September 30, 2015. We recognized impairment charges for goodwill and intangible assets of $7.0 million and $2.6 million in our consolidated statement of operations for the year ended December 31, 2015, respectively.

Amortization expense was approximately $3.3 million, $4.5 million, and $4.4 million for the years ended December 31, 2017, 2016, and 2015, respectively. Our intangible assets related to customer relationships and trade names have an average useful life of 13.6 years. Expected amortization expense for each of the next five years and thereafter is as follows (in thousands):



Year Ended	Amount
2018	$	2,658
2019	2,658
2020	2,658
2021	2,658
2022	2,658
Thereafter	13,314
	$	26,604