Debt - Revolving Credit Agreements (Details) $ in Millions	6 Months Ended
	Jun. 30, 2021 USD ($)	Jul. 20, 2021
Subsequent event
Line of Credit Facility [Line Items]
Consolidated leverage ratio		3.75
TDS Revolving credit facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 400
Letters of credit outstanding	1
Amount borrowed	125
Amount available for use	$ 274
TDS Revolving credit facility | LIBOR rate
Line of Credit Facility [Line Items]
Contractual spread	1.50%
UScellular Revolving credit facility | UScellular
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 300
Letters of credit outstanding	0
Amount borrowed	0
Amount available for use	$ 300