Intangible Assets

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Identifiable intangible assets consisted of the following at December 31:



(In millions)	Gross Carrying Amount		Accumulated Amortization		Net Book Value
2019	Gross Carrying Amount		Accumulated Amortization		Net Book Value
Customer relationships	$	16,187	$	2,145	$	14,042
Acquired software and technology	2,607		639		1,968
Trade names	620		105		515
Capitalized software development costs	942		332		610
Purchased software	680		173		507
Total	$	21,036	$	3,394	$	17,642

(In millions)	Gross Carrying Amount		Accumulated Amortization		Net Book Value
2018	Gross Carrying Amount		Accumulated Amortization		Net Book Value
Customer relationships	$	2,642	$	1,294	$	1,348
Acquired software and technology	591		490		101
Trade names	120		71		49
Capitalized software development costs	810		314		496
Purchased software	261		112		149
Total	$	4,424	$	2,281	$	2,143

Gross software development costs capitalized for new products and enhancements to existing products totaled $339 million, $193 million and $159 million in 2019, 2018 and 2017, respectively.

Amortization expense associated with the above identifiable intangible assets was as follows for the years ended December 31:



(In millions)	2019		2018		2017
Amortization expense	$	1,299	$	347	$	326

The Company estimates that annual amortization expense with respect to intangible assets recorded at December 31, 2019 will be as follows:



(In millions)
Year ending December 31,
2020	$	2,490
2021	2,400
2022	2,168
2023	1,891
2024	1,572
Thereafter	7,121
Total	$	17,642