Commitments And Contingencies (Outstanding Performance Letters Of Credit) (Details) $ in Millions	Dec. 31, 2023 USD ($)
FCC Rural Deployment Programs [Member]
Line of Credit Facility [Line Items]
Line of credit, amount outstanding	$ 56
Performance Letters Of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit, amount outstanding	181
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit, amount outstanding	358
Letter of Credit [Member] | Rent Obligations [Member]
Line of Credit Facility [Line Items]
Line of credit, amount outstanding	6
CNA Financial Corporation (CNA) [Member] | Performance Letters Of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit, amount outstanding	29
AIG Insurance [Member] | Performance Letters Of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit, amount outstanding	28
Zurich [Member] | Performance Letters Of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit, amount outstanding	$ 124