Sale of Data Centers and Colocation Business (Details) - USD ($) $ in Millions		3 Months Ended			4 Months Ended	5 Months Ended	6 Months Ended	8 Months Ended	9 Months Ended
	May 01, 2017	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	May 02, 2017	Sep. 30, 2017	Jun. 30, 2017	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense		$ 47		$ 97					$ 214	$ 362
Less assets recorded as part of the failed-sale-leaseback		(41,352)	$ (39,194)			$ (41,352)			(41,352)
Total net amount of assets derecognized		7	2,376			7			7
Capital lease obligations		0	305			0			0
Total net imputed liabilities recognized		0	(419)			0			0
Sale and leaseback transaction loss, net									(82)	$ 0
Colocation Business and Data Centers
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from sales of data centers and colocation business	$ 1,800
Income tax expense			$ 18				$ 47	$ 65
Depreciation and amortization					$ 67
Colocation Business and Data Centers | Disposal group disposed of by sale, not discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill	1,142
Property, plant and equipment	1,051
Other intangible assets	249
Other assets	66
Total net amount of assets derecognized	1,982
Capital lease obligations	294
Other liabilities	274
Total net imputed liabilities recognized	(60)
SIS Holdings, LP | CenturyLink, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
CenturyLink, Inc.'s value of minority stake		150				150			150
Cyxtera Technologies
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense		3							(60)
Less assets recorded as part of the failed-sale-leaseback	526
Less imputed financing obligations from the failed-sale-leaseback	$ (628)
Gain (Loss) on asset leaseback, failed-sale-leaseback transaction									(102)
Sale and leaseback transaction loss, net									(82)
Cyxtera Technologies | Colocation Business and Data Centers | Disposal group disposed of by sale, not discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, gain (loss) on disposal									20
Cyxtera Technologies
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Current amount due from affiliate		$ 80				80			$ 80
Sale-leaseback transaction rent expense						$ 40