Benefit Plans - Pension and postretirement benefits remeasurement gains and losses (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Retirement Benefits [Abstract]
Remeasurement of projected benefit obligation (gains) losses - discount rate	$ 36	$ (265)
Remeasurement of projected benefit obligation (gains) losses - other assumptions	80	(141)
Remeasurement of plan assets (gains) losses	434	(391)
Pension and other postretirement remeasurement (gains) losses	$ 318	$ 15

Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Change in Other Assumptions

No definition available.

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- Definition

Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Change in Weighted Average Discount Rate

+ References

No definition available.

+ Details

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- Definition

Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Remeasurement Plan Assets Gain (Loss)

+ References

No definition available.

+ Details

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- References

No definition available.

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- Definition

Amount of gain (loss), recognized immediately as component of net periodic benefit (cost) credit, for change in value of benefit obligation or plan assets from experience different from that assumed, change in actuarial assumption, or consequence of temporarily deviating from substantive plan. Includes, but is not limited to, amount in excess of ten percent of greater of fair value of plan assets or benefit obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(4)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920

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