Postretirement benefits Schedule of Allocation of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	$ 4,291	$ 3,016
Available for sale, Fair Value	85,488	78,470
Other Investments	6,062	5,277
Fair Value, Recurring [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	2,803	1,575
Available for sale, Fair Value	2,664	3,400
Equity Securities		713
Other Investments	412	381
Fair Value, Recurring [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	1,482	1,440
Available for sale, Fair Value	80,864	73,365
Equity Securities		0
Other Investments	377	303
Fair Value, Recurring [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	6	1
Available for sale, Fair Value	1,960	1,705
Equity Securities		57
Other Investments	10	11
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	95	95
Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	4,921	4,244
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	55	84
Equity Securities	1,467	1,050
Defined benefit plan, fair value of plan assets excluding measured using NAV	2,873	2,290
UNITED STATES | Pension Plan [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	18	10
Equity Securities	1,467	1,050
Defined benefit plan, fair value of plan assets excluding measured using NAV	1,951	1,493
UNITED STATES | Pension Plan [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	37	74
Equity Securities	0	0
Defined benefit plan, fair value of plan assets excluding measured using NAV	922	797
UNITED STATES | Pension Plan [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	0	0
Available for sale, Fair Value	0
Equity Securities	0	0
Defined benefit plan, fair value of plan assets excluding measured using NAV	0	0
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member]
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	600	515
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	466	433
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	134	82
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value		0
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	749	641
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	0	0
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	749	641
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value		0
UNITED STATES | Other Investments [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	428	494
Non - U.S. | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	2	7
Equity Securities	430	474
Defined benefit plan, fair value of plan assets excluding measured using NAV	1,030	899
Non - U.S. | Pension Plan [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	2	7
Equity Securities	112	103
Defined benefit plan, fair value of plan assets excluding measured using NAV	114	110
Non - U.S. | Pension Plan [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	0	0
Equity Securities	318	371
Defined benefit plan, fair value of plan assets excluding measured using NAV	916	789
Non - U.S. | Pension Plan [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Short-term investments	0	0
Equity Securities	0	0
Defined benefit plan, fair value of plan assets excluding measured using NAV	0	0
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	598	418
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	0	0
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	598	418
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	0	0
Non - U.S. | Other Investments [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	107	109
Non - U.S. | Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	4
States, municipalities, and political subdivisions
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	7,515	10,786
States, municipalities, and political subdivisions | Fair Value, Recurring [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	0	0
States, municipalities, and political subdivisions | Fair Value, Recurring [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	7,515	10,786
States, municipalities, and political subdivisions | Fair Value, Recurring [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	0	$ 0
States, municipalities, and political subdivisions | UNITED STATES | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	2
States, municipalities, and political subdivisions | UNITED STATES | Pension Plan [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Available for sale, Fair Value	$ 2