Goodwill, Customer Relationships and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of goodwill, customer relationships and other intangible assets

Goodwill, customer relationships and other intangible assets consisted of the following:

	As of December 31,
	2018		2017
	(Dollars in millions)
Goodwill	$	9,360	9,360
Customer relationships, less accumulated amortization of $4,806 and $4,337	$	893	1,362
Other intangible assets subject to amortization:
Capitalized software, less accumulated amortization of $1,712 and $1,619	$	311	379

Summary of amortization expense

Total amortization expense for intangible assets was as follows:

	Years Ended December 31,
	2018		2017	2016
	(Dollars in millions)
Amortization expense for intangible assets	$	581	671	767

Schedule of estimated amortization expense for intangible assets

We estimate that total amortization expense for intangible assets for the years ending December 31, 2019 through 2023 will be as follows:

	(Dollars in millions)
Year ending December 31,
2019	$	517
2020	453
2021	143
2022	39
2023	27