Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts
Valuation and qualifying accounts
Balance at Beginning of Period	$ 668	$ 594	$ 558
Charged to Costs and Expenses	126	77	37
Charged to Other Accounts	(6)	(3)	(2)
Deductions	0	0	1
Balance at End of Period	788	668	594
Valuation allowance and reserves, current	22	24	18
Environmental, litigation and other reserves
Valuation and qualifying accounts
Balance at Beginning of Period	994	935	997
Charged to Costs and Expenses	182	140	45
Charged to Other Accounts	1,408	85	53
Deductions	(173)	(166)	(160)
Balance at End of Period	2,411	994	935
Valuation allowance and reserves, current	$ 188	$ 146	$ 163