Significant Accounting Policies - Consolidated Statement of Cash Flow as Adjusted (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows from Operating Activities
Net income including noncontrolling interest	$ 1,627	$ 1,310
Company pension and postretirement expense	47	77
Other - net	$ (234)	(452)
Under Prior Method
Cash Flows from Operating Activities
Net income including noncontrolling interest		1,294
Company pension and postretirement expense		98
Other - net		$ (457)