Pension and Other Postretirement Benefits - Fair Values of Pension Plan Assets by Asset Category (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	$ 394,026	$ 361,802
U.S. equities fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	77,687	86,059
Non-U.S. equities fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	77,299	61,630
Government bond fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	64,255	98,418
Corporate bond fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	108,729	82,434
Fixed income fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	16,939	7,320
Liability driven investment fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	22,713	0
Other investments
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	15,103	17,367
Cash & equivalents
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	11,301	8,574
Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	14,451	11,844
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. equities fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	2,913	3,012
Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-U.S. equities fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	6,267	5,602
Quoted Prices in Active Markets for Identical Assets (Level 1) | Government bond fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bond fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed income fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Liability driven investment fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash & equivalents
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	5,271	3,230
Significant Observable Inputs (Level 2)
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	12,238	12,922
Significant Observable Inputs (Level 2) | U.S. equities fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Significant Observable Inputs (Level 2) | Non-U.S. equities fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Significant Observable Inputs (Level 2) | Government bond fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	731	772
Significant Observable Inputs (Level 2) | Corporate bond fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	11,507	12,150
Significant Observable Inputs (Level 2) | Fixed income fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Significant Observable Inputs (Level 2) | Liability driven investment fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Significant Observable Inputs (Level 2) | Other investments
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Significant Observable Inputs (Level 2) | Cash & equivalents
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	0	0
Fair Value Measured at Net Asset Value Per Share
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	367,337	337,036
Fair Value Measured at Net Asset Value Per Share | U.S. equities fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	74,774	83,047
Fair Value Measured at Net Asset Value Per Share | Non-U.S. equities fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	71,032	56,028
Fair Value Measured at Net Asset Value Per Share | Government bond fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	63,524	97,646
Fair Value Measured at Net Asset Value Per Share | Corporate bond fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	97,222	70,284
Fair Value Measured at Net Asset Value Per Share | Fixed income fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	16,939	7,320
Fair Value Measured at Net Asset Value Per Share | Liability driven investment fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	22,713	0
Fair Value Measured at Net Asset Value Per Share | Other investments
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	15,103	17,367
Fair Value Measured at Net Asset Value Per Share | Cash & equivalents
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	6,030	$ 5,344
Significant Unobservable Inputs (Level 3)
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	367,337
Significant Unobservable Inputs (Level 3) | U.S. equities fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	74,774
Significant Unobservable Inputs (Level 3) | Non-U.S. equities fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	71,032
Significant Unobservable Inputs (Level 3) | Government bond fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	63,524
Significant Unobservable Inputs (Level 3) | Corporate bond fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	97,222
Significant Unobservable Inputs (Level 3) | Fixed income fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	16,939
Significant Unobservable Inputs (Level 3) | Liability driven investment fund
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	22,713
Significant Unobservable Inputs (Level 3) | Other investments
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	15,103
Significant Unobservable Inputs (Level 3) | Cash & equivalents
Pension And Other Employee Benefit Plans [Line Items]
Fair values of pension plan assets by asset category	$ 6,030