Goodwill and other intangible assets (Tables)

3 Months Ended

Mar. 31, 2013

Reconciliation of the change in goodwill

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

	March 31,			December 31,
	2013			2012
Balance at beginning of year	$	54,523		$	53,213
Acquisitions of businesses		14			1,442
Other, including foreign currency translation		(130	)		(132	)
Balance at end of period	$	54,407		$	54,523

Schedule of intangible assets

Intangible assets other than goodwill are included in other assets in our Consolidated Balance Sheets and are summarized by type as follows (in millions).

	March 31, 2013				December 31, 2012
	Gross carrying amount		Accumulated amortization		Gross carrying amount		Accumulated amortization
Insurance and other	$	11,669	$	3,143	$	11,737	$	2,994
Railroad, utilities and energy		2,163		990		2,163		913
	$	13,832	$	4,133	$	13,900	$	3,907
Trademarks and trade names	$	2,799	$	293	$	2,819	$	278
Patents and technology		5,005		2,179		5,014		2,059
Customer relationships		4,532		1,241		4,565		1,155
Other		1,496		420		1,502		415
	$	13,832	$	4,133	$	13,900	$	3,907