Goodwill, Customer Relationships and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

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,
	2017		2016
	(Dollars in millions)
Goodwill	$	9,360	9,354
Customer relationships, less accumulated amortization of $4,337 and $3,822	$	1,362	1,877
Other intangible assets subject to amortization:
Capitalized software, less accumulated amortization of $1,619 and $1,510	$	379	471

Summary of amortization expense

Total amortization expense for intangible assets was as follows:

	Years Ended December 31,
	2017		2016	2015
	(Dollars in millions)
Amortization expense for intangible assets	$	671	767	871

Schedule of estimated amortization expense for intangible assets

We estimate that total amortization expense for intangible assets for the years ending December 31, 2018 through 2022 will be as follows:

	(Dollars in millions)
Year ending December 31,
2018	$	583
2019	513
2020	446
2021	136
2022	32