Segment Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting, Revenue Reconciling Item [Line Items]
Goodwill	$ 7,736		$ 7,736		$ 7,749
Assets	24,746		24,746		24,017
Payments to Acquire Productive Assets	364	$ 328	1,028	$ 899
Adjusted EBITDA by Segment	716	657	2,141	1,957
Revenue	2,033	2,062	6,140	6,176
Income Tax Expense	(74)	(16)	(198)	(39)
Other Expenses	(137)	(310)	(465)	(844)
Depreciation, Depletion and Amortization	(319)	(296)	(930)	(872)
Share-based Compensation	(43)	(34)	(121)	(92)
Net Income (Loss) Available to Common Stockholders, Basic	143	1	427	110
Goodwill, Translation Adjustments			(13)
Corporate and Other [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Assets	130		130		129
Payments to Acquire Productive Assets	37	37	116	103
Adjusted EBITDA by Segment	(204)	(244)	(654)	(723)
North America [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Goodwill	7,024		7,024		7,024
Assets	20,618		20,618		19,961
Payments to Acquire Productive Assets	245	202	677	560
Adjusted EBITDA by Segment	784	760	2,415	2,267
Goodwill, Translation Adjustments			0
EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Goodwill	116		116		129
Assets	1,760		1,760		1,796
Payments to Acquire Productive Assets	38	41	117	114
Adjusted EBITDA by Segment	56	63	162	176
Goodwill, Translation Adjustments			(13)
Latin America [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Goodwill	596		596		596
Assets	2,238		2,238		$ 2,131
Payments to Acquire Productive Assets	44	48	118	122
Adjusted EBITDA by Segment	80	78	218	237
Goodwill, Translation Adjustments			0
Core Network Service [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	1,930	1,945	5,833	5,814
Core Network Service [Member] \| North America [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	1,572	1,551	4,778	4,636
Core Network Service [Member] \| EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	182	211	564	623
Core Network Service [Member] \| Latin America [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	176	183	491	555
Wholesale Voice Services [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	103	117	307	362
Wholesale Voice Services [Member] \| North America [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	99	110	293	342
Wholesale Voice Services [Member] \| EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	2	3	8	10
Wholesale Voice Services [Member] \| Latin America [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 2	$ 4	$ 6	$ 10

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Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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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.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

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