Significant Accounting Policies - Consolidated Statement of Cash Flow as Adjusted (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Cash Flows from Operating Activities
Net income including noncontrolling interest	$ 1,525	$ 1,303	$ 3,152	$ 2,613
Company pension and postretirement expense			92	155
Other - net			$ (80)	(376)
Under Prior Method
Cash Flows from Operating Activities
Net income including noncontrolling interest		$ 1,287		2,581
Company pension and postretirement expense				197
Other - net				$ (386)