Intangible Assets

9 Months Ended

Sep. 30, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Identifiable intangible assets consisted of the following:



(In millions)	Gross Carrying Amount		Accumulated Amortization		Net Book Value
September 30, 2019	Gross Carrying Amount		Accumulated Amortization		Net Book Value
Customer relationships	$	16,220	$	1,680	$	14,540
Acquired software and technology	2,227		556		1,671
Trade names	586		75		511
Capitalized software development costs	950		355		595
Purchased software	557		137		420
Total	$	20,540	$	2,803	$	17,737



(In millions)	Gross Carrying Amount		Accumulated Amortization		Net Book Value
December 31, 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

The Company estimates that annual amortization expense with respect to acquired intangible assets recorded at September 30, 2019, which include customer relationships, acquired software and technology, and trade names, will be approximately $1.0 billion in 2019, $2.1 billion in 2020, $2.1 billion in 2021, $1.9 billion in 2022, and $1.8 billion in 2023. Amortization expense with respect to capitalized and purchased software recorded at September 30, 2019 is estimated to approximate $270 million in 2019.