Equipment held for lease - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Depreciation expense for equipment held for lease	$ 1,181	$ 1,102	$ 751
Sales and service revenues	176,512	175,445
Insurance and Other [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease revenues	5,856	5,732	2,452
Fixed lease revenue	4,415
Variable lease revenue	1,441
Sales and service revenues	$ 134,989	133,336	$ 130,343
Insurance and Other [Member] | ASC 606 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease revenues		3,280
Sales and service revenues		$ (3,280)