v3.20.4

Pension and Postretirement Benefits (Weighted Average Assumptions - Projected Benefit Obligation And Net Pension And Postemployment Benefit Cost) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Sep. 30, 2019 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |
Composite rate of compensation increase for determining benefit obligation | 3.00% |  |  |  |  | 3.00% | 3.00% |
Pension Benefits |  |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |
Weighted-average discount rate for determining benefit obligation at December 31 | 3.40% |  |  |  |  | 2.70% | 3.40% | 4.50%
Weighted-average interest credit rate for cash balance pension programs | 3.30% |  |  |  |  | 3.10% | 3.30% | 3.70%
Long-term rate of return on plan assets |  |  |  |  |  | 7.00% | 7.00% | 7.00%
Composite rate of compensation increase for determining benefit obligation | 3.00% |  |  |  |  | 3.00% | 3.00% | 3.00%
Composite rate of compensation increase for determining net cost (benefit) |  |  |  |  |  | 3.00% | 3.00% | 3.00%
Assumptions used, percentage change in weighted-average interest crediting rate that would impact pension benefit obligation |  |  |  |  |  | 0.50% |  |
Effect of 0.50% increase in weighted-average interest crediting rate, increase to pension benefit obligation |  |  |  |  |  | $ 130 |  |
Pension Benefits | Service Cost |  |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |
Discount rate in effect for determining net cost | 3.50% | 3.90% | 4.30% | 4.60% |  | 3.60% | 4.10% | 4.20%
Pension Benefits | Interest Cost |  |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |
Discount rate in effect for determining net cost | 3.00% | 3.20% | 3.70% | 4.20% |  | 2.90% | 3.50% | 3.80%
Postretirement Benefits |  |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |
Weighted-average discount rate for determining benefit obligation at December 31 | 3.20% |  |  |  |  | 2.40% | 3.20% | 4.40%
Weighted-average interest credit rate for cash balance pension programs | 0.00% |  |  |  |  | 0.00% | 0.00% | 0.00%
Long-term rate of return on plan assets |  |  |  |  |  | 4.75% | 5.75% | 5.75%
Composite rate of compensation increase for determining benefit obligation | 3.00% |  |  |  |  | 3.00% | 3.00% | 3.00%
Composite rate of compensation increase for determining net cost (benefit) |  |  |  |  |  | 3.00% | 3.00% | 3.00%
Postretirement Benefits | Service Cost |  |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |
Discount rate in effect for determining net cost | 3.40% |  |  |  | 4.70% | 3.50% | 4.40% | 4.30%
Postretirement Benefits | Interest Cost |  |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |  |
Discount rate in effect for determining net cost | 2.70% |  |  |  | 4.00% | 2.70% | 3.70% | 3.60%

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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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