

4.	Wireless Licenses, Goodwill and Other Intangible Assets

Wireless Licenses

The carrying amount of Wireless licenses are as follows:

During the nine months ended September 30, 2018, we recorded approximately $4.5 billion of wireless licenses in connection with the Straight Path acquisition and $0.7 billion in connection with the NextLink acquisition. See Note 3 for additional information.

At September 30, 2018 and December 31, 2017, approximately $11.1 billion and $8.8 billion, respectively, of wireless licenses were under development for commercial service for which we were capitalizing interest costs. We recorded approximately $0.4 billion of capitalized interest on wireless licenses for both the nine months ended September 30, 2018 and 2017.

The average remaining renewal period for our wireless licenses portfolio was 4.8 years as of September 30, 2018.

Goodwill

Changes in the carrying amount of Goodwill are as follows:



(dollars in millions)	Wireless		Wireline			Other			Total
Balance at January 1, 2018	$	18,397	$	3,955		$	6,820		$	29,172
Acquisitions (Note 3)	—		(82		)	225			143
Reclassifications, adjustments and other	—		(4		)	(111		)	(115		)
Balance at September 30, 2018	$	18,397	$	3,869		$	6,934		$	29,200

During the nine months ended September 30, 2018, a goodwill impairment charge of $0.1 billion related to early-stage development companies was recorded in Selling, general and administrative expense in our condensed consolidated statement of income.

Other Intangible Assets

The following table displays the composition of Other intangible assets, net:



	At September 30, 2018							At December 31, 2017
(dollars in millions)	Gross Amount		Accumulated Amortization			Net Amount		Gross Amount		Accumulated Amortization			Net Amount
Customer lists (8 to 13 years)	$	3,623	$	(945	)	$	2,678	$	3,621	$	(691	)	$	2,930
Non-network internal-use software (3 to 7 years)	18,901		(13,371		)	5,530		18,010		(12,374		)	5,636
Other (2 to 25 years)	2,484		(961		)	1,523		2,474		(793		)	1,681
Total	$	25,008	$	(15,277	)	$	9,731	$	24,105	$	(13,858	)	$	10,247

The amortization expense for Other intangible assets was as follows:



	Three Months Ended		Nine Months Ended
(dollars in millions)	September 30,		September 30,
2018	$	557	$	1,648
2017	536		1,473

The estimated future amortization expense for Other intangible assets is as follows:



Years	(dollars in millions)
Remainder of 2018	$	557
2019	2,027
2020	1,692
2021	1,400
2022	1,149
2023	871

At September 30,

At December 31,

(dollars in millions)

Wireless licenses