Current Expected Credit Loss (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Cumulative effect of accounting change	$ (94)
Notes and accounts receivable, net of allowances - Financial Instruments under Topic 326	17,740
Notes and accounts receivable, allowances - Financial Instruments under Topic 326	148
Loans and long term receivables, net of allowances - Financial Instruments under Topic 326	9,211
Loans and long term receivables, allowances - Financial Instruments under Topic 326	441
ExxonMobil Share Of Earnings Reinvested [Member]
Cumulative effect of accounting change	$ (93)