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Nonqualified Benefit Plans Investments (Details 16) - Unfunded Plan - Supplemental Employee Retirement Plan - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
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Defined Benefit Plan Disclosure [Line Items] |  |
Investments in nonqualified benefit plans | $ 148,800 | $ 134,118
Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Investments in nonqualified benefit plans | 100,104 | 87,009
Life insurance carried on plan participants |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Investments in nonqualified benefit plans | 39,779 | 38,659
Other Investments |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Investments in nonqualified benefit plans | $ 8,917 | $ 8,450

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