Goodwill and other intangible assets (Tables)

3 Months Ended

Mar. 31, 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).

	March 31, 2018		December 31, 2017
Balance at beginning of year	$	81,258	$	79,486
Acquisitions of businesses		52		1,545
Other, including foreign currency translation		27		227
Balance at end of period	$	81,337	$	81,258

Schedule of intangible assets

Other intangible assets are summarized as follows (in millions).

	March 31, 2018				December 31, 2017
	Gross carrying amount		Accumulated amortization		Gross carrying amount		Accumulated amortization
Insurance and other	$	40,317	$	8,057	$	40,225	$	7,707
Railroad, utilities and energy		993		334		988		324
	$	41,310	$	8,391	$	41,213	$	8,031
Trademarks and trade names	$	5,394	$	710	$	5,381	$	692
Patents and technology		4,383		2,579		4,341		2,493
Customer relationships		28,353		3,943		28,322		3,722
Other		3,180		1,159		3,169		1,124
	$	41,310	$	8,391	$	41,213	$	8,031