Investments, Advances And Long-Term Receivables (Details) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments, Advances And Long-Term Receivables [Abstract]
Investments (Companies carried at equity in underlying assets)		$ 26,382	$ 24,354	$ 20,810
Advances (Companies carried at equity in underlying assets)		8,608	9,112
Total equity company investments and advances		34,990	33,466
Equity securities carried at fair value and other investments at adjusted cost basis	[1]	210	174
Long-term receivables and miscellaneous, net of reserves of $5,471 million and $5,432 million		5,590	5,520
Total		40,790	39,160
Reserves for long-term receivables and miscellaneous investments		$ 5,471	$ 5,432

[1] Effective January 1, 2018, ExxonMobil adopted the Financial Accounting Standards Board’s Update, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The portion of unrealized gains and losses recognized during the reporting period on equity securities still held at December 31, 2018, and the carrying value of equity securities without readily determinable fair values at December 31, 2018, were not significant to the Corporation.