Sale of Data Centers and Colocation Business (Details) - USD ($) $ in Millions		3 Months Ended			4 Months Ended	6 Months Ended	8 Months Ended		12 Months Ended
	May 01, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	May 02, 2017	Jun. 30, 2017	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax (benefit) expense									$ (849)	$ 394	$ 438
Less assets not removed as a result of the failed-sale-leaseback				$ (39,194)			$ (51,204)		(51,204)	(39,194)
Total net amount of assets derecognized				2,376			140		140	2,376
Capital lease obligations				305			0		0	305
Total net imputed liabilities recognized				(419)			0		0	(419)
Sale and leaseback transaction loss, net									(82)	$ 0	$ 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 colocation business and data centers	$ 1,800
Income tax (benefit) expense				$ 18		$ 47		$ 65
Total net amount of assets derecognized							1,982		1,982
Total net imputed liabilities recognized							(60)		(60)
Depreciation and amortization			$ 50		$ 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
Capital lease obligations	294
Other liabilities	274
SIS Holdings, LP | CenturyLink, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noncontrolling Interest in Limited Partnerships							150		150
Cyxtera Technologies
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax (benefit) expense									(65)
Less assets not removed as a result 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		$ (119)							(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							49		$ 49
Sale-leaseback transaction rent expense							$ 80