Goodwill and other intangible assets (Tables)

12 Months Ended

Dec. 31, 2020

Goodwill And Intangible Assets Disclosure [Abstract]

Reconciliation of the change in goodwill

Reconciliations of the changes in the carrying value of goodwill during 2020 and 2019 follows (in millions).

	December 31,
	2020			2019
Balance at beginning of year	$	81,882		$	81,025
Acquisitions of businesses		1,758			890
Impairment charges		(10,033	)		(90	)
Other, including foreign currency translation		127			57
Balance at end of year*	$	73,734		$	81,882

* Net of accumulated goodwill impairments of $11.0 billion as of December 31, 2020 and $1.1 billion as of December 31, 2019.

Schedule of intangible assets

The gross carrying amounts and related accumulated amortization of other intangible assets are summarized as follows (in millions).

	December 31, 2020				December 31, 2019
	Gross carrying amount		Accumulated amortization		Gross carrying amount		Accumulated amortization
Insurance and other:
Customer relationships	$	27,374	$	5,756	$	27,943	$	5,025
Trademarks and trade names		5,206		779		5,286		759
Patents and technology		4,766		3,313		4,560		3,032
Other		3,339		1,375		3,364		1,286
	$	40,685	$	11,223	$	41,153	$	10,102
Railroad, utilities and energy:
Customer relationships	$	678	$	361	$	678	$	324
Trademarks, trade names and other		1,003		98		325		84
	$	1,681	$	459	$	1,003	$	408