Sale Of Equipment Installment Receivables (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Changes In Other Assets [Line Items]
Other Assets - current	$ 12,008		$ 10,757
Accounts payable and accrued liabilities	31,569		34,470
Outstanding derecognized receivables	8,895		7,446
Guarantee Obligations [Member]
Changes In Other Assets [Line Items]
Accounts payable and accrued liabilities	94		55
Guarantee Obligation, current	309		204
Deferred Purchase Price [Member]
Changes In Other Assets [Line Items]
Other Assets	3,009		2,749
Other Assets - current	1,996		1,781
Finance Receivables [Member]
Changes In Other Assets [Line Items]
Other Assets	4,798		6,079
Cash proceeds from sale of receivables, net	2,395	$ 1,432
Repurchased Installment Receivables	0	$ 377
Finance Receivables [Member] | Notes Receivable [Member]
Changes In Other Assets [Line Items]
Gross equipment installment receivables balance - current	$ 2,627		$ 3,340