Background and Summary of Significant Accounting Policies - Additional Information (Details) $ / shares in Units, shares in Millions, $ in Millions				3 Months Ended	12 Months Ended
	Jan. 01, 2019 USD ($)	Oct. 31, 2018 reporting_unit	Oct. 31, 2017 reporting_unit	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) reporting_unit $ / shares shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Finite-Lived Intangible Assets [Line Items]
Advertising expense					$ 98	$ 218	$ 216
Accounts receivable, past due threshold					30 days
Reclassification from AOCI to retained earnings, tax effect				$ 407
Number of reporting units | reporting_unit		5	3		5
Goodwill impairment					$ 2,726	0	0
Capitalized labor and related costs					$ 569	559	524
Minimum
Finite-Lived Intangible Assets [Line Items]
Contract term					1 year
Customer relationship period for revenue recognition					10 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Contract term					7 years
Customer relationship period for revenue recognition					20 years
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life					7 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life					15 years
Capitalized software
Finite-Lived Intangible Assets [Line Items]
Estimated useful life					7 years
Integrated billing and customer care system
Finite-Lived Intangible Assets [Line Items]
Estimated useful life					20 years
Finite-lived intangible assets, gross					$ 237
Other intangible assets | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life					4 years
Other intangible assets | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life					20 years
Common Stock
Finite-Lived Intangible Assets [Line Items]
Unissued shares of CenturyLink common stock | shares					4
Nonredeemable Preferred Stock
Finite-Lived Intangible Assets [Line Items]
Redemption price (in dollars per share) | $ / shares					$ 25
Stock compensation plan | Common Stock
Finite-Lived Intangible Assets [Line Items]
Unissued shares of CenturyLink common stock | shares					30
Accounting Standards Update 2016-02 | Subsequent event
Finite-Lived Intangible Assets [Line Items]
Sale leaseback transaction, deferred gain, gross	$ 115
Term of recognition	3 years
Accounting Standards Update 2016-02 | Minimum | Subsequent event
Finite-Lived Intangible Assets [Line Items]
Right-of-use asset	$ 1,900
Operating lease, liability	1,900
Accounting Standards Update 2016-02 | Maximum | Subsequent event
Finite-Lived Intangible Assets [Line Items]
Right-of-use asset	2,200
Operating lease, liability	$ 2,200
Retained Earnings | Accounting Standards Update 2014-09
Finite-Lived Intangible Assets [Line Items]
Cumulative effect of adoption					$ 338	0	0
Cumulative net effect of adoption of ASU, tax					$ 119	$ 0	$ 0
Consumer Customers | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Length of customer life					30 months
Business Customer
Finite-Lived Intangible Assets [Line Items]
Length of customer life					49 months
Business Customer | Minimum
Finite-Lived Intangible Assets [Line Items]
Length of customer life					12 months
Business Customer | Maximum
Finite-Lived Intangible Assets [Line Items]
Length of customer life					60 months