Goodwill and other intangible assets (Tables)

9 Months Ended

Sep. 30, 2017

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).

	September 30,  2017		December 31,  2016
Balance at beginning of year	$	79,486	$	62,708
Acquisitions of businesses		1,199		17,650
Other, including foreign currency translation		197		(872	)
Balance at end of period	$	80,882	$	79,486

Schedule of intangible assets

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

	September 30, 2017				December 31, 2016
	Gross carrying amount		Accumulated amortization		Gross carrying amount		Accumulated amortization
Insurance and other	$	40,528	$	7,554	$	39,976	$	6,495
Railroad, utilities and energy		974		323		898		293
	$	41,502	$	7,877	$	40,874	$	6,788
Trademarks and trade names	$	5,352	$	672	$	5,175	$	616
Patents and technology		4,487		2,605		4,341		2,328
Customer relationships		28,497		3,517		28,243		2,879
Other		3,166		1,083		3,115		965
	$	41,502	$	7,877	$	40,874	$	6,788