Postretirement Benefits - Pension Assets by Components at Fair Value (Details) - Pension Plan - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 523,099	$ 499,775
Percentage of plan assets	100.00%	100.00%
Investment funds, percentage ownership by pension plan		1.00%	1.00%
Expected life of investment	2 years	3 years
Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 509,332	$ 485,487
Percentage of plan assets	97.00%	97.00%
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 311,873	$ 269,311
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	197,459	216,176
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 13,767	$ 14,288
Percentage of plan assets	3.00%	3.00%
Total corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 77,317	$ 128,647
Percentage of total plan assets, within plan asset category	15.00%	26.00%
Total corporate bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 0	$ 0
Total corporate bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	77,317	128,647
Total corporate bonds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Financial
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 22,482	$ 35,649
Percentage of total plan assets, within plan asset category	4.00%	7.00%
Financial | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 0	$ 0
Financial | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	22,482	35,649
Financial | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Utilities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 20,838	$ 23,436
Percentage of total plan assets, within plan asset category	4.00%	5.00%
Utilities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 0	$ 0
Utilities | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	20,838	23,436
Utilities | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Energy
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 7,564	$ 12,776
Percentage of total plan assets, within plan asset category	2.00%	3.00%
Energy | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 0	$ 0
Energy | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	7,564	12,776
Energy | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Other corporates
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 26,433	$ 56,786
Percentage of total plan assets, within plan asset category	5.00%	11.00%
Other corporates | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 0	$ 0
Other corporates | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	26,433	56,786
Other corporates | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 276,478	$ 258,297
Percentage of total plan assets, within plan asset category	53.00%	52.00%
Exchange traded funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 276,478	$ 258,297
Exchange traded funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Exchange traded funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
U.S. Government and Agency
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 76,643	$ 44,213
Percentage of total plan assets, within plan asset category	15.00%	9.00%
U.S. Government and Agency | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 0	$ 0
U.S. Government and Agency | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	76,643	44,213
U.S. Government and Agency | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Other bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 202	$ 200
Percentage of total plan assets, within plan asset category	0.00%	0.00%
Other bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 0	$ 0
Other bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	202	200
Other bonds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Guaranteed annuity contract
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 43,297	$ 43,116
Percentage of total plan assets, within plan asset category	8.00%	8.00%
Guaranteed annuity contract | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 0	$ 0
Guaranteed annuity contract | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	43,297	43,116
Guaranteed annuity contract | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 23,016	$ 4,467
Percentage of total plan assets, within plan asset category	4.00%	1.00%
Short-term investments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 23,016	$ 4,467
Short-term investments | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Short-term investments | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 12,379	$ 6,547
Percentage of total plan assets, within plan asset category	2.00%	1.00%
Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 12,379	$ 6,547
Other | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	0	0
Other | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, within plan asset category	$ 0	$ 0