Intangible Assets

6 Months Ended

Jun. 30, 2017

Intangible Assets, Net (Excluding Goodwill) [Abstract]

Intangible Assets

Intangible Assets

The following table summarizes the components of our intangible assets at the dates indicated:

	June 30, 2017						December 31, 2016
	Gross Carrying Amount		Accumulated Amortization		Carrying Value		Gross Carrying Amount		Accumulated Amortization		Carrying Value
Refinery Services:
Customer relationships	$	94,654	$	91,125	$	3,529	$	94,654	$	89,756	$	4,898
Licensing agreements	38,678		35,366		3,312		38,678		34,204		4,474
Segment total	133,332		126,491		6,841		133,332		123,960		9,372
Onshore Facilities & Transportation:
Customer relationships	35,430		34,379		1,051		35,430		33,676		1,754
Intangibles associated with lease	13,260		4,696		8,564		13,260		4,459		8,801
Segment total	48,690		39,075		9,615		48,690		38,135		10,555
Marine contract intangibles	27,000		9,000		18,000		27,000		6,300		20,700
Offshore pipeline contract intangibles	158,101		15,949		142,152		158,101		11,788		146,313
Other	28,816		12,035		16,781		28,569		10,622		17,947
Total	$	395,939	$	202,550	$	193,389	$	395,692	$	190,805	$	204,887

Our amortization of intangible assets for the periods presented was as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Amortization of intangible assets	$	5,872	$	6,040	$	11,744	$	12,032

We estimate that our amortization expense for the next five years will be as follows:

Remainder of	2017	$	11,842
	2018	$	21,513
	2019	$	17,178
	2020	$	16,241
	2021	$	10,634