Other Intangible Assets and Liabilities

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



	As of March 31, 2016				As of December 31, 2015
	Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
Intangible assets	$	660	$	202	$	660	$	192
Intangible liabilities	$	1,403	$	761	$	1,403	$	736

As of March 31, 2016 and December 31, 2015, 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):



	Three Months Ended March 31,
	2016		2015
Amortization of intangible assets	$	10	$	31
Amortization of intangible liabilities	$	25	$	34

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
Remainder of 2016	$	29	$	76
2017	$	36	$	96
2018	$	33	$	90
2019	$	31	$	27
2020	$	31	$	26