Accounting Policies and Supplemental Disclosures - Use of Estimates (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Property, Plant and Equipment [Line Items]
Decrease in depreciation and amortization	$ (6,523)	$ (5,563)	$ (17,633)	$ (15,619)	$ (23,803)		$ (19,881)
Increase in net income	$ 6,331	$ 2,134	$ 14,109	$ 8,320	$ 17,377		$ 11,347
Increase in basic earnings per share	$ 12.63	$ 4.31	$ 28.24	$ 16.87
Increase in diluted earnings per share	$ 12.37	$ 4.23	$ 27.72	$ 16.53
Technology equipment
Property, Plant and Equipment [Line Items]
Useful life of equipment			4 years			3 years
Change in equipment useful life
Property, Plant and Equipment [Line Items]
Decrease in depreciation and amortization	$ 634		$ 2,100
Increase in net income	$ 479		$ 1,600
Increase in basic earnings per share	$ 0.95		$ 3.23
Increase in diluted earnings per share	$ 0.93		$ 3.18