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Retirement Plans (Plan's Allocated Target Ranges and Actual Weighted Average Asset Allocation by Investment Categories) (Details) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018
Percent Hedge Against Projected Benefit Obligation |  | 57.00% |
Actual percentage |  | 100.00% | 100.00%
Return Seeking Assets [Member] |  |  |
Actual percentage | [1] | 59.00% | 43.00%
Liability Hedging Assets [Member] |  |  |
Actual percentage |  | 38.00% | 38.00%
Short-term Investments [Member] |  |  |
Actual percentage |  | 3.00% | 19.00%
Minimum [Member] | Return Seeking Assets [Member] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description |  | 0.15 |
Minimum [Member] | Liability Hedging Assets [Member] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description |  | 0.35 |
Minimum [Member] | Short-term Investments [Member] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description |  | 0 |
Maximum [Member] | Return Seeking Assets [Member] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description |  | 0.7 |
Maximum [Member] | Liability Hedging Assets [Member] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description |  | 0.75 |
Maximum [Member] | Short-term Investments [Member] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description |  | 0 |
[1] | Includes limited partnerships.

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- Definition Description of investment policy and strategy for defined benefit plan asset. Includes, but is not limited to, investment allocation decision and factor pertinent to understanding investment policy and strategy for plan asset. Factor includes, but is not limited to, investment goal, risk management practice, permitted and prohibited investment including use of derivative, diversification, and relationship between plan asset and obligation. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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