Sale Of Equipment Installment Receivables (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts payable and accrued liabilities	$ 42,306		$ 43,184
Outstanding derecognized receivables	10,863		9,065
Guarantee Obligations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts payable and accrued liabilities	160		196
Guarantee Obligation, current	430		439
Notes Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross equipment installment receivables balance - current	3,072		3,457
Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other Assets	6,611		5,994
Supplemental Deferred Purchase Price	309	$ 519
Cash proceeds received on finance receivables, net of remittances	8,387
Other Assets [Member] | WarnerMedia [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Pledged Assets, Not Separately Reported, Finance Receivables	1,402
Other Assets [Member] | Deferred Purchase Price [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other Assets	2,240		2,370
Other Assets [Member] | Finance Receivables [Member] | WarnerMedia [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other Assets	1,400
Other Current Assets [Member] | Deferred Purchase Price [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Supplemental Deferred Purchase Price	$ 1,418		$ 1,448