Goodwill and other intangible assets (Tables)

12 Months Ended

Dec. 31, 2011

Reconciliation of the change in goodwill

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

	December 31,
	2011		2010
Balance at beginning of year	$	49,006	$	33,972
Acquisition of businesses		4,179		15,069
Other		28		(35	)
Balance at end of year	$	53,213	$	49,006

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).

	December 31, 2011				December 31, 2010
	Gross carrying amount		Accumulated amortization		Gross carrying amount		Accumulated amortization
Insurance and other	$	11,016	$	2,319	$	6,944	$	1,816
Railroad, utilities and energy		2,088		623		2,082		306
	$	13,104	$	2,942	$	9,026	$	2,122
Trademarks and trade names	$	2,655	$	219	$	2,027	$	166
Patents and technology		4,900		1,496		2,922		1,013
Customer relationships		4,060		840		2,676		612
Other		1,489		387		1,401		331
	$	13,104	$	2,942	$	9,026	$	2,122