Intangible Assets

6 Months Ended

Jun. 30, 2014

Goodwill and Intangible Assets Disclosure [Abstract]

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



	As of June 30, 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	$	(51	)	$	19	$	70	$	(48	)	$	22
Other	9		(7		)	2		9		(6		)	3
Total	$	79	$	(58	)	$	21	$	79	$	(54	)	$	25

Total amortization expense was $2 million and $4 million for the first three and six months, respectively, of each of 2014 and 2013. 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	$	3	$	7	$	7	$	2	$	1	$	1

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



	As of June 30, 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

Intangible assets are included in other assets on our consolidated balance sheets, except for approximately $5 million of other indefinite-lived intangible assets which met the criteria to be classified as held for sale during the second quarter of 2014 and therefore are included in other current assets on our consolidated balance sheet as of June 30, 2014.