Goodwill and Other Intangible Assets and Liabilities

During the years ended December 31, 2017, 2016 and 2015, no impairment losses related to goodwill were incurred. As of December 31, 2017 and 2016, there were no accumulated impairment losses related to goodwill. For both the years ended December 31, 2017 and 2016, the carrying values were $14,845 million and no additional goodwill was recognized.

Intangible assets and liabilities were as follows (in millions):



	As of December 31, 2017				As of December 31, 2016
	Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
Intangible assets	$	647	$	253	$	661	$	231
Intangible liabilities	$	1,403	$	932	$	1,403	$	836

As of December 31, 2017 and 2016, intangible assets primarily consisted of franchise and customer assets. Intangible liabilities primarily consisted of customer and shortline contracts which were in an unfavorable position at the date of Merger.

Amortizable intangible assets and liabilities are amortized based on the estimated pattern in which the economic benefits are expected to be consumed or on a straight-line basis over their estimated economic lives.

Amortization of intangible assets and liabilities was as follows (in millions):



	December 31, 2017		December 31, 2016		December 31, 2015
Amortization of intangible assets	$	36	$	39	$	58
Amortization of intangible liabilities	$	96	$	100	$	115

Amortization of intangible assets and liabilities for the next five years is expected to approximate the following (in millions):



	Amortization of intangible assets		Amortization of intangible liabilities
2018	$	33	$	90
2019	$	31	$	27
2020	$	31	$	26
2021	$	31	$	24
2022	$	31	$	23