Background and Summary of Significant Accounting Policies - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) state	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Deferred Revenue Arrangement [Line Items]
Number of states in which entity operates | state	14
Advertising Costs
Advertising expense	$ 28	$ 58	$ 139
Accounts Receivable and Allowance for Doubtful Accounts
Threshold for determining accounts receivable as past due, days outstanding	30 days
Minimum
Revenue Recognition
Contract term	1 year
Customer relationship period for revenue recognition	10 years
Maximum
Revenue Recognition
Contract term	5 years
Customer relationship period for revenue recognition	20 years
Pension, Supplemental and Other Postretirement Benefit Plans | Qwest Communications International, Inc.
Affiliate Transactions
Repayments on affiliate obligation	$ 76	$ 87
Payment term		30 years
Consumer Customers | Average
Revenue Recognition
Customer life	30 months
Business Customer
Revenue Recognition
Customer life	49 months
Business Customer | Minimum
Revenue Recognition
Customer life	49 months