Accounting Policies Revenue, Initial Application Period Cumulative Effect Transition (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net service sales	$ 19,437	$ 11,980
Net product sales	31,605	23,734
Cost of sales	30,735	$ 22,440
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Subscription Services [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net service sales	845
Net product sales	(845)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Other Services [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net service sales	560
Cost of sales	$ 560