Preparation Of Interim Financial Statements (Consolidated Statements of Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other cost of services	$ 7,932	$ 9,288
Selling, general and administrative	7,897	8,772
Operating Income (Loss)	6,201	6,356
Other income (expense) - net	1,702	488
Net income	4,759	3,574
Historical Accounting Method [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other cost of services	7,572
Selling, general and administrative	6,755
Operating Income (Loss)	7,703
Other income (expense) - net	200
Net income	4,759
Historical Accounting Method, previously reported [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other cost of services		9,065
Selling, general and administrative		8,487
Operating Income (Loss)		6,864
Other income (expense) - net		(20)
Net income		3,574
Effect of Adoption | ASU 2017-07
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other cost of services	360	223
Selling, general and administrative	1,142	285
Operating Income (Loss)	(1,502)	(508)
Other income (expense) - net	1,502	508
Net income	$ 0	$ 0