Quarterly Financial Data (Unaudited) (Details) - USD ($)	3 Months Ended								4 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	May 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 19, 2017
Operating revenues by products and services
Operating revenue	$ 5,778,000,000	$ 5,818,000,000	$ 5,902,000,000	$ 5,945,000,000	$ 5,323,000,000	$ 4,034,000,000	$ 4,090,000,000	$ 4,209,000,000		$ 23,443,000,000	$ 17,656,000,000	$ 17,470,000,000
Operating income (loss)	(1,841,000,000)	894,000,000	767,000,000	750,000,000	524,000,000	487,000,000	367,000,000	631,000,000		570,000,000	2,009,000,000	2,333,000,000
Net (loss) income	$ (2,412,000,000)	$ 272,000,000	$ 292,000,000	$ 115,000,000	$ 1,117,000,000	$ 92,000,000	$ 17,000,000	$ 163,000,000		$ (1,733,000,000)	$ 1,389,000,000	$ 626,000,000
Basic (loss) earnings per common share (in dollars per share)	$ (2.26)	$ 0.25	$ 0.27	$ 0.11	$ 1.26	$ 0.17	$ 0.03	$ 0.30		$ (1.63)	$ 2.21	$ 1.16
Diluted (loss) earnings per common share (in dollars per share)	$ (2.26)	$ 0.25	$ 0.27	$ 0.11	$ 1.26	$ 0.17	$ 0.03	$ 0.30		$ (1.63)	$ 2.21	$ 1.16
Goodwill impairment										$ 2,726,000,000	$ 0	$ 0
Acquisition related costs	$ 117,000,000	$ 43,000,000	$ 162,000,000	$ 71,000,000	$ 206,000,000	$ 37,000,000	$ 18,000,000	$ 10,000,000
Provisional tax benefit, amount											$ 1,100,000,000
Statutory federal income tax rate										21.00%	35.00%	35.00%
Term Loan B
Operating revenues by products and services
Interest expense related to Term loan B					$ 20,000,000	$ 44,000,000
Term Loan B | Medium-term Notes | CenturyLink Escrow, LLC
Operating revenues by products and services
Debt instrument, face amount													$ 6,000,000,000
Cyxtera Technologies
Operating revenues by products and services
Operating revenue										$ 74,000,000	$ 49,000,000
Net (loss) income										(21,000,000)	(103,000,000)
Gain (Loss) on asset leaseback, failed-sale-leaseback transaction							(119,000,000)			(102,000,000)
Depreciation expense on reclassified assets							$ 44,000,000			$ 0	$ 44,000,000
Colocation Business and Data Centers
Operating revenues by products and services
Depreciation and amortization								$ 50,000,000	$ 67,000,000