Pension and Postretirement Benefit Plans - Components of net periodic benefit cost and other information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net periodic benefit cost (benefit)
Net periodic benefit cost (benefit)	$ (17)	$ 1	$ (34)	$ (35)
Funded | Postretirement Benefits
Net periodic benefit cost (benefit)
Service cost	11	11	22	22
Interest cost	16	21	32	42
Expected return on plan assets	(20)	(21)	(40)	(41)
Amortization of prior service benefit	(8)	(7)	(16)	(14)
Amortization of net actuarial loss	12	8	24	17
Settlements, curtailments, special terminations and other	1		2
Total non-operating expense (benefit)	1	1	2	4
Net periodic benefit cost (benefit)	12	12	24	26
Funded | United States | Qualified and Non-qualified Pension Benefits
Net periodic benefit cost (benefit)
Service cost	65	63	131	125
Interest cost	126	156	250	311
Expected return on plan assets	(255)	(260)	(510)	(520)
Amortization of prior service benefit	(6)	(6)	(12)	(12)
Amortization of net actuarial loss	134	92	268	183
Settlements, curtailments, special terminations and other		35		35
Total non-operating expense (benefit)	(1)	17	(4)	(3)
Net periodic benefit cost (benefit)	64	80	127	122
Funded | International | Qualified and Non-qualified Pension Benefits
Net periodic benefit cost (benefit)
Service cost	38	33	76	66
Interest cost	33	39	64	78
Expected return on plan assets	(77)	(75)	(154)	(150)
Amortization of transition asset			1
Amortization of prior service benefit	(2)	(3)	(3)	(6)
Amortization of net actuarial loss	31	19	62	39
Settlements, curtailments, special terminations and other		1		1
Total non-operating expense (benefit)	(15)	(19)	(30)	(38)
Net periodic benefit cost (benefit)	$ 23	$ 14	$ 46	$ 28