Goodwill and other intangible assets (Tables)

6 Months Ended

Jun. 30, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Reconciliation of the change in goodwill

A reconciliation of the change in the carrying value of goodwill is as follows (in millions).

	June 30, 2018		December 31, 2017
Balance at beginning of year	$	81,258	$        79,486
Acquisitions of businesses		177	1,545
Other, including foreign currency translation		(185)	227
Balance at end of period	$	81,250	$        81,258

Schedule of intangible assets

Other intangible assets are summarized as follows (in millions).
	June 30, 2018				December 31, 2017
	Gross carrying amount		Accumulated amortization		Gross carrying amount		Accumulated amortization
Insurance and other	$	40,267	$	8,342	$	40,225	$          7,707
Railroad, utilities and energy		1,018		349		988	324
	$	41,285	$	8,691	$	41,213	$          8,031
Trademarks and trade names	$	5,398	$	729	$	5,381	$             692
Patents and technology		4,380		2,635		4,341	2,493
Customer relationships		28,335		4,140		28,322	3,722
Other		3,172		1,187		3,169	1,124
	$	41,285	$	8,691	$	41,213	$          8,031