General - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ 1,292	$ 1,006
Pension and other postretirement remeasurement gains and losses	15	14
Income taxes	303	189
Other operating assets and liabilities	(410)	(371)
Net cash provided by operating activities	714	626
Previously reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	1,287	975
Pension and other postretirement remeasurement gains and losses	0	0
Income taxes	302	181
Other operating assets and liabilities	(389)	(318)
Net cash provided by operating activities	714	626
Impact of change | Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	5	31
Pension and other postretirement remeasurement gains and losses	(15)	14
Income taxes	1	8
Other operating assets and liabilities	21	(53)
Net cash provided by operating activities	$ 0	$ 0