Intangible Assets - Definite-Lived Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets
Definite-lived intangible assets, gross carrying value	$ 976	$ 976
Accumulated amortization	(845)	(828)
Marketing agreements
Finite-Lived Intangible Assets
Definite-lived intangible assets, gross carrying value	730	730
Accumulated amortization	(677)	(667)
Contracts
Finite-Lived Intangible Assets
Definite-lived intangible assets, gross carrying value	193	193
Accumulated amortization	(115)	(108)
Other
Finite-Lived Intangible Assets
Definite-lived intangible assets, gross carrying value	53	53
Accumulated amortization	$ (53)	$ (53)

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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