Other Long-Term Assets, Net

Other long-term assets, net of accumulated amortization, consisted of the following (in millions):



	December 31,
	2017			2016
Intangible assets ⁽¹⁾	$	1,265		$	603
Other	60			48
	1,325			651
Accumulated amortization	(421		)	(361		)
	$	904		$	290


⁽¹⁾	We include rights-of-way, which are intangible assets, in our pipeline and related facilities amounts within property and equipment. See Note 5 for a discussion of property and equipment.

The increase in intangible assets for the year ended December 31, 2017 was primarily due to acreage dedication contracts and associated customer relationships associated with our ACC Acquisition. See Note 6 for additional information. Amortization expense for finite-lived intangible assets for the years ended December 31, 2017, 2016 and 2015 was $54 million, $44 million and $49 million, respectively.

Intangible assets that have finite lives are tested for impairment when events or circumstances indicate that the carrying value may not be recoverable. We did not recognize any impairments of finite-lived intangible assets during the three years ended December 31, 2017. Our intangible assets that have finite lives consisted of the following (in millions):



		December 31, 2017							December 31, 2016
	Estimated Useful Lives (Years)	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Customer contracts and relationships	1 – 20	$	1,188	$	(383	)	$	805	$	529	$	(330	)	$	199
Property tax abatement	7 – 13	38		(30		)	8		38		(26		)	12
Other agreements	25 – 70	39		(8		)	31		36		(5		)	31
		$	1,265	$	(421	)	$	844	$	603	$	(361	)	$	242

We estimate that our amortization expense related to finite-lived intangible assets for the next five years will be as follows (in millions):



2018	$	63
2019	$	68
2020	$	74
2021	$	75
2022	$	76