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Employee Benefit Plans, Fair Values of Pension Plan Assets (Details) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Period to keep distributions in immediately available funds |  | 1 year |  |
Defined Benefit Pension Plans Combined [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets |  | $ 56,315 | $ 49,349 | $ 40,624
Defined Benefit Pension Plans Combined [Member] | Cash and Money Market Funds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [1] | 624 | 682 |
Defined Benefit Pension Plans Combined [Member] | Common Equity Securities [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [2] | 0 | 662 |
Defined Benefit Pension Plans Combined [Member] | Equity Mutual Funds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [3] | 35,707 | 29,677 |
Defined Benefit Pension Plans Combined [Member] | U.S. Treasury Obligations [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets |  | 631 | 615 |
Defined Benefit Pension Plans Combined [Member] | Corporate and Foreign Bonds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [4] | 5,615 | 6,078 |
Defined Benefit Pension Plans Combined [Member] | Fixed Income Mutual Funds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [5] | 13,738 | 11,635 |
Defined Benefit Pension Plans Combined [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets |  | 50,069 | 42,656 |
Defined Benefit Pension Plans Combined [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash and Money Market Funds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [1] | 624 | 682 |
Defined Benefit Pension Plans Combined [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Common Equity Securities [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [2] | 0 | 662 |
Defined Benefit Pension Plans Combined [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Funds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [3] | 35,707 | 29,677 |
Defined Benefit Pension Plans Combined [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury Obligations [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets |  | 0 | 0 |
Defined Benefit Pension Plans Combined [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate and Foreign Bonds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [4] | 0 | 0 |
Defined Benefit Pension Plans Combined [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed Income Mutual Funds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [5] | 13,738 | 11,635 |
Defined Benefit Pension Plans Combined [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets |  | 6,246 | 6,693 |
Defined Benefit Pension Plans Combined [Member] | Significant Other Observable Inputs (Level 2) [Member] | Cash and Money Market Funds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [1] | 0 | 0 |
Defined Benefit Pension Plans Combined [Member] | Significant Other Observable Inputs (Level 2) [Member] | Common Equity Securities [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [2] | 0 | 0 |
Defined Benefit Pension Plans Combined [Member] | Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [3] | 0 | 0 |
Defined Benefit Pension Plans Combined [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury Obligations [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets |  | 631 | 615 |
Defined Benefit Pension Plans Combined [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate and Foreign Bonds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [4] | 5,615 | 6,078 |
Defined Benefit Pension Plans Combined [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fixed Income Mutual Funds [Member] |  |  |  |
Fair Value of Pension Plan Assets [Abstract] |  |  |  |
Fair value of plan assets | [5] | $ 0 | $ 0 |
[1] | The portfolios are designed to keep up to one year of distributions in immediately available funds.
[2] | This category includes investments in U.S. common stocks and foreign stocks trading in the U.S. widely distributed among consumer discretionary, consumer staples, healthcare, information technology, financial services, telecommunications, industrials, real estate, materials, and energy. The individual stocks are primarily large cap stocks which track with the S&P 500.
[3] | This category currently includes a majority of investments in closed-end mutual funds as well as domestic equity mutual funds and international mutual funds which give the portfolio exposure to mid and large cap index funds as well as international diversified index funds.
[4] | This category currently includes only U.S. corporate bonds and notes widely distributed among consumer discretionary, consumer staples, healthcare, information technology, energy, transportation, and financial services.
[5] | This category includes fixed income investments in mutual funds which include government, corporate and mortgage securities of both the U.S. and other countries. The mortgage-backed securities and non-U.S. corporate and sovereign investments add further diversity to the fixed income portion of the portfolio.

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- Definition Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee. + 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 (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 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/disclosureRef -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/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 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 7: 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 + Details
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- Definition Period of time to keep distributions from the defined benefit plan in immediately available funds, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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