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Employee Postretirement Benefits - Allocation of Plan Assets (Details) - USD ($) $ in Thousands | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | $ 313,798 | $ 387,212
Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 310,095 | 374,415
Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
NAV |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 3,703 | 12,797
Equity Funds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 124,327 | 149,479
Equity Funds | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 124,327 | 149,479
Equity Funds | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
Equity Funds | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
Equity Funds | NAV |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
Fixed Income Funds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 156,424 | 184,987
Fixed Income Funds | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 156,424 | 184,987
Fixed Income Funds | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
Fixed Income Funds | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
Fixed Income Funds | NAV |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
Hybrid Funds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 9,756 | 11,776
Hybrid Funds | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 9,756 | 11,776
Hybrid Funds | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
Hybrid Funds | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
Hybrid Funds | NAV |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
U.S. Treasury Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 19,588 | 28,173
U.S. Treasury Securities | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 19,588 | 28,173
U.S. Treasury Securities | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
U.S. Treasury Securities | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
U.S. Treasury Securities | NAV |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
SEI Energy Debt Collective Fund |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 3,703 | 12,797
SEI Energy Debt Collective Fund | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
SEI Energy Debt Collective Fund | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
SEI Energy Debt Collective Fund | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | 0 | 0
SEI Energy Debt Collective Fund | NAV |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan Assets | $ 3,703 | $ 12,797

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