Investments in Unconsolidated Businesses - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Dividends and repatriations of foreign earnings received	$ 0us-gaap_InvestmentIncomeDividend	$ 0us-gaap_InvestmentIncomeDividend	$ 400,000,000us-gaap_InvestmentIncomeDividend
Goodwill	24,639,000,000us-gaap_Goodwill	24,634,000,000us-gaap_Goodwill	24,139,000,000us-gaap_Goodwill
Vodafone Omnitel N.V.
Schedule of Equity Method Investments [Line Items]
Goodwill		$ 1,100,000,000

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant