Goodwill and other intangible assets (Tables)

9 Months Ended

Sep. 30, 2020

Goodwill And Intangible Assets Disclosure [Abstract]

Reconciliation of the change in goodwill

Reconciliations of the changes in the carrying value of goodwill for the first nine months of 2020 and for the year ended December 31, 2019 follow (in millions).

	September 30, 2020			December 31, 2019
Balance at beginning of year	$	81,882		$	81,025
Acquisitions of businesses		25			890
Impairment charges		(10,021	)		—
Other, including foreign currency translation		(21	)		(33	)
Balance at end of period	$	71,865		$	81,882

Schedule of intangible assets

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

	September 30, 2020				December 31, 2019
	Gross carrying amount		Accumulated amortization		Gross carrying amount		Accumulated amortization
Insurance and other:
Customer relationships	$	27,344	$	5,548	$	27,943	$	5,025
Trademarks and trade names		5,193		774		5,286		759
Patents and technology		4,720		3,255		4,560		3,032
Other		3,319		1,347		3,364		1,286
	$	40,576	$	10,924	$	41,153	$	10,102
Railroad, utilities and energy:
Customer relationships	$	678	$	352	$	678	$	324
Trademarks, trade names and other		325		91		325		84
	$	1,003	$	443	$	1,003	$	408