Pension and Postretirement Benefit Plans and Defined Contribution Plans - Healthcare Cost Trend Rate Assumptions (Details) - Postretirement Benefits Plan [Member] |
12 Months Ended | |
|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
|
| Defined Benefit Plan Disclosure [Line Items] | ||
| Healthcare cost trend rate assumed for next year (up to age 65) | 5.40% | 5.60% |
| Healthcare cost trend rate assumed for next year (age 65 and older) | 5.60% | 6.00% |
| Rate to which the cost trend rate is assumed to decline | 4.50% | 4.50% |