Goodwill and other intangible assets

12 Months Ended

Dec. 31, 2019

Goodwill And Intangible Assets Disclosure [Abstract]

(13)	Goodwill and other intangible assets

Reconciliations of the changes in the carrying value of goodwill during 2019 and 2018 follows (in millions).

	December 31,
	2019			2018
Balance at beginning of year	$	81,025		$	81,258
Acquisitions of businesses		890			376
Other, including foreign currency translation		(33	)		(609	)
Balance at end of year	$	81,882		$	81,025

Notes to Consolidated Financial Statements (Continued)

(13)	Goodwill and other intangible assets (Continued)

Our other intangible assets and related accumulated amortization are summarized as follows (in millions).

	December 31, 2019				December 31, 2018
	Gross carrying amount		Accumulated amortization		Gross carrying amount		Accumulated amortization
Insurance and other:
Trademarks and trade names	$	5,286	$	759	$	5,152	$	727
Patents and technology		4,560		3,032		4,446		2,790
Customer relationships		27,943		5,025		27,697		4,287
Other		3,364		1,286		3,198		1,190
	$	41,153	$	10,102	$	40,493	$	8,994

Railroad, utilities and energy:
Trademarks and trade names	$	212	$	26	$	216	$	23
Customer relationships		678		324		678		286
Other		113		58		117		53
	$	1,003	$	408	$	1,011	$	362

Intangible asset amortization expense was $1,317 million in 2019, $1,393 million in 2018 and $1,469 million in 2017. Estimated amortization expense over the next five years is as follows (in millions): 2020 – $1,275; 2021 – $1,144; 2022 – $1,082; 2023 – $993 and 2024 – $913. Intangible assets with indefinite lives were $19.0 billion as of December 31, 2019 and $18.9 billion as of December 31, 2018 and primarily related to certain customer relationships and trademarks and trade names.