Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2015

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 June 30, 2015							As of December 31, 2014
(millions)	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
Intangible Assets with Definite Lives:
Customer relationships	$	70	$	(58	)	$	12	$	70	$	(54	)	$	16
Other	9		(7		)	2		9		(7		)	2
Total	$	79	$	(65	)	$	14	$	79	$	(61	)	$	18

Estimated annual amortization expense intangible assets

Estimated amortization expense for the remainder of 2015 and for future years is as follows:

(millions)	2015		2016		2017		2018 and thereafter
Estimated future amortization expense	$	4	$	7	$	2	$	1

Schedule of indefinite-lived intangible assets

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

	As of June 30, 2015							As of December 31, 2014
(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	9		(1		)	8		9		(1		)	8
Total	$	31	$	(1	)	$	30	$	31	$	(1	)	$	30