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Sale Of Equipment Installment Receivables (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Changes In Other Assets [Line Items]
Other Assets - current	$ 16,278		$ 16,278		$ 10,757
Accounts payable and accrued liabilities	39,375		39,375		34,470
Outstanding derecognized receivables	8,428		8,428		7,446
Guarantee Obligations [Member]
Changes In Other Assets [Line Items]
Accounts payable and accrued liabilities	230		230		55
Guarantee Obligation, current	418		418		204
Deferred Purchase Price [Member]
Changes In Other Assets [Line Items]
Other Assets	1,981		1,981		2,749
Other Current Assets [Member]
Changes In Other Assets [Line Items]
Other Assets - current	1,114		1,114		1,781
Finance Receivables [Member]
Changes In Other Assets [Line Items]
Other Assets	5,736		5,736		6,079
Cash proceeds from sale of receivables, net	1,752	$ 1,292	5,679	$ 4,139
Repurchased Installment Receivables	0	$ 567	1,481	$ 1,281
Finance Receivables [Member] \| Notes Receivable [Member]
Changes In Other Assets [Line Items]
Gross equipment installment receivables balance - current	$ 3,370		3,370		$ 3,340
Finance Receivables, Net [Member]
Changes In Other Assets [Line Items]
Cash proceeds from sale of receivables, net			$ 6,267