Sale Of Equipment Installment Receivables (Finance Receivables) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Finance Receivables [Member]
Changes In Other Assets [Line Items]
Receivables sold during period		$ 2,161	$ 1,619	$ 7,077	$ 6,217
Cash proceeds received		1,752	1,292	5,679	4,139
Deferred purchase price recorded		335	285	1,161	1,767
Guarantee obligation recorded		75	65	270	139
Finance Receivables Net [Member]
Changes In Other Assets [Line Items]
Receivables sold during period	[1]	$ 2,064	$ 1,478	6,670	$ 5,698
Cash proceeds received				$ 6,267

[1] Receivables net of allowance, imputed interest and trade-in right guarantees.