Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2013

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Finite-Lived Intangible Assets

Intangible assets with definite lives are amortized. These assets are summarized as follows:

	As of December 31, 2013							As of December 31, 2012
(millions)	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
Intangible Assets with Definite Lives:
Customer relationships	$	70	$	(48	)	$	22	$	70	$	(41	)	$	29
Other	9		(6		)	3		9		(6		)	3
Total	$	79	$	(54	)	$	25	$	79	$	(47	)	$	32

Estimated Annual Amortization Expense Intangible Assets

Estimated annual amortization expense is as follows:

(millions)	2014		2015		2016		2017		2018 and thereafter
Estimated annual amortization expense	$	7	$	7	$	7	$	2	$	2

Schedule of Indefinite-Lived Intangible Assets

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

	As of December 31, 2013						As of December 31, 2012
(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		1		7		8		—		8
Total	$	30	$	1	$	29	$	30	$	—	$	30