Stockholder's Equity (Details) - USD ($) $ in Millions		12 Months Ended
	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stockholder's Equity (Deficit)
Common stock, shares issued (in shares)		1	1
Common stock, shares outstanding (shares)		1	1
Dividends
Dividends declared to QSC		$ 1,275	$ 1,000	$ 1,300
Cash dividend paid to QSC		$ 1,275	$ 1,000	$ 1,300
Dividend of equity interest in limited liability company to Qwest Services Corporation	$ 12
COMMON STOCK
Stockholder's Equity (Deficit)
Common stock, shares issued (in shares)		1
Common stock, shares outstanding (shares)		1