Intangible Assets (Tables)

3 Months Ended

Mar. 31, 2014

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets with definitive lives

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

	As of March 31, 2014							As of December 31, 2013
(millions)	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
Intangible Assets with Definite Lives:
Customer relationships	$	70	$	(50	)	$	20	$	70	$	(48	)	$	22
Other	9		(6		)	3		9		(6		)	3
Total	$	79	$	(56	)	$	23	$	79	$	(54	)	$	25

Estimated annual amortization expense intangible assets

Estimated amortization expense for the remainder of 2014 and for future years is as follows:

(millions)	2014		2015		2016		2017		2018		2019 and thereafter
Estimated future amortization expense	$	5	$	7	$	7	$	2	$	1	$	1

Schedule of indefinite-lived intangible assets

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

	As of March 31, 2014						As of December 31, 2013
(millions)	Gross Carrying Amount		Accumulated Impairment Charges		Net		Gross Carrying Amount		Accumulated Impairment Charges		Net
Intangible Assets with Indefinite Lives:
Trade names	$	22	$	—	$	22	$	22	$	—	$	22
Other	8		1		7		8		1		7
Total	$	30	$	1	$	29	$	30	$	1	$	29