Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2012

Intangible Assets [Abstract]

Intangible assets with definitive lives

	As of June 30, 2012							As of December 31, 2011
(millions)	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
Intangible Assets with Definite Lives:
Customer relationships	$	70	$	(37	)	$	33	$	70	$	(34	)	$	36
Other		9		(6	)		3		9		(5	)		4
Total	$	79	$	(43	)	$	36	$	79	$	(39	)	$	40

Estimated annual amortization expense intangible assets

	2012		2013		2014		2015		2016		2017 and thereafter
(millions)
Estimated future amortization expense	$	4	$	7	$	7	$	7	$	7	$	4

Intangible Assets with Indefinite Lives

	As of June 30, 2012						As of December 31, 2011
(millions)	Gross Carrying Amount		Impairment Charges		Net		Gross Carrying Amount		Impairment Charges		Net
Intangible Assets with Indefinite Lives:
Trade names	$	22	$	—	$	22	$	22	$	—	$	22
Other		8		—		8		8		—		8
Total	$	30	$	—	$	30	$	30	$	—	$	30