Goodwill and other intangible assets (Tables)

9 Months Ended

Sep. 30, 2016

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,  2016		December 31,  2015
Balance at beginning of year	$	62,708	$	60,714
Acquisitions of businesses		17,016		2,563
Other, including foreign currency translation		(332)		(569)
Balance at end of period	$	79,392	$	62,708

Schedule of intangible assets

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

	September 30, 2016						December 31, 2015
	Gross carrying amount			Accumulated amortization			Gross carrying amount			Accumulated amortization
Insurance and other		$	41,575		$	6,541		$	14,610		$	5,462
Railroad, utilities and energy			897			279			888			239
		$	42,472		$	6,820		$	15,498		$	5,701
Trademarks and trade names		$	6,049		$	821		$	3,041		$	765
Patents and technology			4,455			2,329			4,252			2,050
Customer relationships			28,851			2,721			5,474			2,131
Other			3,117			949			2,731			755
		$	42,472		$	6,820		$	15,498		$	5,701