Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2014

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of intangible assets with definite lives

These assets are summarized as follows:

	As of December 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	$	(54	)	$	16	$	70	$	(48	)	$	22
Other	9		(7		)	2		9		(6		)	3
Total	$	79	$	(61	)	$	18	$	79	$	(54	)	$	25

Schedule of estimated annual amortization expense

Estimated annual amortization expense is as follows:

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

Schedule of intangible assets with indefinite lives

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

	As of December 31, 2014						As of December 31, 2013
(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	9		1		8		8		1		7
Total	$	31	$	1	$	30	$	30	$	1	$	29