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Benefit Plans - Additional Disclosures (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Other Postretirement Benefit Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Company Contributions | $ 0 | $ 0
Current plus 1 | 0 |
Actual Benefit Payments for the Year Ending: Current | 1,975 |
Expected Benefit Payments for the Year Ending: Current plus 1 | 1,765 |
Expected Benefit Payments for the Year Ending: Current plus 2 | 1,995 |
Expected Benefit Payments for the Year Ending: Current plus 3 | 2,157 |
Expected Benefit Payments for the Year Ending: Current plus 4 | 2,241 |
Expected Benefit Payments for the Year Ending: Current plus 5 | 2,357 |
Expected Benefit Payments for the Year Ending: Current plus 6 - 10 | $ 10,916 |
Other Postretirement Benefit Plan | Equity securities | Minimum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocations (in hundredths) | 70.00% |
Other Postretirement Benefit Plan | Equity securities | Maximum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocations (in hundredths) | 100.00% |
Other Postretirement Benefit Plan | Real Estate | Minimum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocations (in hundredths) | 0.00% |
Other Postretirement Benefit Plan | Real Estate | Maximum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocations (in hundredths) | 15.00% |
Other Postretirement Benefit Plan | Commodities | Minimum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocations (in hundredths) | 0.00% |
Other Postretirement Benefit Plan | Commodities | Maximum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocations (in hundredths) | 10.00% |
Other Postretirement Benefit Plan | Fixed Income/Cash | Minimum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocations (in hundredths) | 0.00% |
Other Postretirement Benefit Plan | Fixed Income/Cash | Maximum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocations (in hundredths) | 10.00% |
Pension and Supplemental Executive Retirement Plans |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Company Contributions | $ 12,453 | $ 10,205
Current plus 1 | 6,200 |
Actual Benefit Payments for the Year Ending: Current | 46,213 |
Expected Benefit Payments for the Year Ending: Current plus 1 | 30,082 |
Expected Benefit Payments for the Year Ending: Current plus 2 | 29,929 |
Expected Benefit Payments for the Year Ending: Current plus 3 | 30,076 |
Expected Benefit Payments for the Year Ending: Current plus 4 | 29,567 |
Expected Benefit Payments for the Year Ending: Current plus 5 | 28,852 |
Expected Benefit Payments for the Year Ending: Current plus 6 - 10 | $ 135,830 |

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- Definition The amount of payments made from the benefit fund and company funds for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. May also include payments made under a postretirement benefit plan. This item represents a periodic decrease to the plan obligations and a decrease to plan assets. + References No definition available. + Details
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- Definition Amount of contribution received by defined benefit plan from employer which increases plan assets. + 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/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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