Sale Of Equipment Installment Receivables (Finance Receivables) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Finance Receivables [Member]
Changes In Other Assets [Line Items]
Receivables sold during period		$ 3,010	$ 2,846
Cash proceeds received		2,395	1,432
Deferred purchase price recorded		519	1,189
Guarantee obligation recorded		123	0
Finance Receivables Net [Member]
Changes In Other Assets [Line Items]
Receivables sold during period	[1]	$ 2,795	$ 2,621

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