Intangible Assets

6 Months Ended

Jun. 30, 2011

Intangible Assets [Abstract]

Intangible assets

7. Intangible Assets

Intangible assets are included in other assets on the condensed consolidated balance sheets. Intangible assets with definite lives are amortized. These assets are summarized as follows:

	As of June 30, 2011							As of December 31, 2010
	Gross							Gross
	Carrying		Accumulated					Carrying		Accumulated
(millions)	Amount		Amortization			Net		Amount		Amortization			Net
Intangible Assets with Definite Lives:
Customer relationships	$	70	$	(30	)	$	40	$	70	$	(26	)	$	44
Other		9		(5	)		4		9		(5	)		4
Total	$	79	$	(35	)	$	44	$	79	$	(31	)	$	48

     Total amortization expense was $2 million and $4 million for second quarter and first six months of 2011, respectively, and $2 million and $4 million for second quarter and first six months of 2010, respectively. Estimated annual amortization expense is as follows:

(millions)	2011		2012		2013		2014		2015		2016
Estimated annual amortization expense	$	8	$	8	$	7	$	7	$	7	$	7

     Intangible assets with indefinite lives are not amortized. These assets are summarized as follows:

	As of June 30, 2011						As of December 31, 2010
	Gross						Gross
	Carrying		Impairment				Carrying		Impairment
(millions)	Amount		Charges		Net		Amount		Charges			Net
Intangible Assets with Indefinite Lives:
Trade names	$	22	$	—	$	22	$	22	$	—		$	22
Other		8		—		8		9		(1	)		8
Total	$	30	$	—	$	30	$	31	$	(1	)	$	30