Goodwill and other intangible assets (Tables)

12 Months Ended

Dec. 31, 2012

Reconciliation of the change in goodwill

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

	December 31,
	2012			2011
Balance at beginning of year	$	53,213		$	49,006
Acquisitions of businesses		1,442			4,179
Other, including foreign currency translation		(132	)		28
Balance at end of year	$	54,523		$	53,213

Schedule of intangible assets

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

	December 31, 2012				December 31, 2011
	Gross carrying amount		Accumulated amortization		Gross carrying amount		Accumulated amortization
Insurance and other	$	11,737	$	2,994	$	11,016	$	2,319
Railroad, utilities and energy		2,163		913		2,088		623
	$	13,900	$	3,907	$	13,104	$	2,942
Trademarks and trade names	$	2,819	$	278	$	2,655	$	219
Patents and technology		5,014		2,059		4,900		1,496
Customer relationships		4,565		1,155		4,060		840
Other		1,502		415		1,489		387
	$	13,900	$	3,907	$	13,104	$	2,942