Other Financial Information Other Financial Information (Details) (Wireless spectrum licenses, USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Nov. 03, 2014
Wireless spectrum licenses
Schedule of Impaired Long-Lived Assets Held for Sale [Line Items]
Impairment of intangible assets, indefinite-lived (excluding goodwill)	$ (14)
Disposed long-lived assets, contract sales price		$ 39

Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16373-109275

Name:	us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration