Goodwill and other intangible assets (Tables)

3 Months Ended

Mar. 31, 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).

	March 31, 2016			December 31, 2015
Balance at beginning of year	$	62,708		$	60,714
Acquisitions of businesses		16,617			2,563
Other, including foreign currency translation		(211	)		(569)
Balance at end of period	$	79,114		$	62,708

Schedule of intangible assets

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

	March 31, 2016						December 31, 2015
	Gross carrying amount			Accumulated amortization			Gross carrying amount			Accumulated amortization
Insurance and other		$	41,073		$	5,806		$	14,610		$	5,462
Railroad, utilities and energy			892			252			888			239
		$	41,965		$	6,058		$	15,498		$	5,701
Trademarks and trade names		$	6,036		$	782		$	3,041		$	765
Patents and technology			4,332			2,148			4,252			2,050
Customer relationships			28,504			2,304			5,474			2,131
Other			3,093			824			2,731			755
		$	41,965		$	6,058		$	15,498		$	5,701