Goodwill and Intangibles

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangibles

Goodwill and Intangibles

Goodwill

The carrying amount of goodwill by segment at December 31 was:

	Millions of Dollars
	Midstream		Refining	Marketing and Specialties	Total
Balance at January 1, 2017	$	626	1,805	839	3,270
Adjustments	—		—	—	—
Balance at December 31, 2017	626		1,805	839	3,270
Adjustments	—		—	—	—
Balance at December 31, 2018	$	626	1,805	839	3,270

Intangible Assets

The gross carrying value of indefinite-lived intangible assets at December 31 consisted of the following:

	Millions of Dollars
	2018		2017
Trade names and trademarks	$	503	503
Refinery air and operating permits	250		252
Other	—		1
	$	753	756

The net book value of our amortized intangible assets was $116 million and $120 million at December 31, 2018 and 2017, respectively. Acquisitions of amortized intangible assets were not material in 2018 and 2017. For the years ended December 31, 2018, 2017 and 2016, amortization expense was $14 million, $21 million and $18 million, respectively, and is expected to be less than $20 million per year in future years.