Current Expected Credit Loss (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($)
Cumulative effect of accounting change	$ (94)
Notes and accounts receivable, net of allowances - Financial Instruments under Topic 326	15,519
Notes and accounts receivable, allowances - Financial Instruments under Topic 326	153
Loans and long term receivables, net of allowances - Financial Instruments under Topic 326	9,434
Loans and long term receivables, allowances - Financial Instruments under Topic 326	443
ExxonMobil Share Of Earnings Reinvested [Member]
Cumulative effect of accounting change	$ (93)