Pension and other postretirement benefits - Fair values of pension plan assets (Detail) - USD ($) $ in Thousands | 12 Months Ended | |
Dec. 31, 2022 | Dec. 31, 2021 |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Maximum percentage of net assets invested in emerging market | 35% | |
Minimum | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Effective average duration to maintain | 3 years | |
Maximum | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Effective average duration to maintain | 10 years | |
Emerging markets debt fund | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Percentage of net assets invested in foreign equity securities | 80% | |
Small and Mid-Sized Companies | Equity Securities | U.S. Russell 2500 Index | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Percentage of net assets invested | 80% | |
Foreign Companies | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Percentage of net assets invested in foreign equity securities | 80% | |
Fair Value, Measurements, Recurring | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | $ 357,270 | $ 469,793 |
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 357,270 | 459,105 |
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 287,004 | 439,093 |
Fair Value, Measurements, Recurring | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 59,152 | 879 |
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 11,114 | 19,133 |
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | | 10,688 |
Fair Value, Measurements, Recurring | Cash | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 769 | 923 |
Fair Value, Measurements, Recurring | Cash | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 769 | 923 |
Fair Value, Measurements, Recurring | Cash | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Cash | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Money market funds | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 13 | 6 |
Fair Value, Measurements, Recurring | Money market funds | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 13 | 6 |
Fair Value, Measurements, Recurring | Money market funds | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Money market funds | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Managed Volatility | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 46,721 | 57,252 |
Fair Value, Measurements, Recurring | Managed Volatility | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 46,721 | 57,252 |
Fair Value, Measurements, Recurring | Managed Volatility | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Managed Volatility | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | U.S. Small/Mid-Cap Equity | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 6,054 | 7,532 |
Fair Value, Measurements, Recurring | U.S. Small/Mid-Cap Equity | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 6,054 | 7,532 |
Fair Value, Measurements, Recurring | U.S. Small/Mid-Cap Equity | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | U.S. Small/Mid-Cap Equity | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | World equity (excluding U.S.) | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 28,159 | 34,287 |
Fair Value, Measurements, Recurring | World equity (excluding U.S.) | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 28,159 | 34,287 |
Fair Value, Measurements, Recurring | World equity (excluding U.S.) | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | World equity (excluding U.S.) | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Intermediate duration bond fund | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 105,865 | 101,363 |
Fair Value, Measurements, Recurring | Intermediate duration bond fund | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 105,865 | 101,363 |
Fair Value, Measurements, Recurring | Intermediate duration bond fund | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Intermediate duration bond fund | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Long duration bond fund | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 87,018 | 171,919 |
Fair Value, Measurements, Recurring | Long duration bond fund | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 87,018 | 171,919 |
Fair Value, Measurements, Recurring | Long duration bond fund | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Long duration bond fund | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Corporate bond fund | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 6,092 | 7,607 |
Fair Value, Measurements, Recurring | Corporate bond fund | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 6,092 | 7,607 |
Fair Value, Measurements, Recurring | Corporate bond fund | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Corporate bond fund | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Emerging markets debt fund | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 6,284 | 7,605 |
Fair Value, Measurements, Recurring | Emerging markets debt fund | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 6,284 | 7,605 |
Fair Value, Measurements, Recurring | Emerging markets debt fund | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Emerging markets debt fund | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Corporate, government and foreign bonds | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 58,572 | 50,599 |
Fair Value, Measurements, Recurring | Corporate, government and foreign bonds | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 50,599 |
Fair Value, Measurements, Recurring | Corporate, government and foreign bonds | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 58,572 | 0 |
Fair Value, Measurements, Recurring | Corporate, government and foreign bonds | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Absolute return credit fund | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 427 | 671 |
Fair Value, Measurements, Recurring | Absolute return credit fund | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Absolute return credit fund | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 427 | 671 |
Fair Value, Measurements, Recurring | Absolute return credit fund | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Asset backed – home loans | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 153 | 208 |
Fair Value, Measurements, Recurring | Asset backed – home loans | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Asset backed – home loans | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 153 | 208 |
Fair Value, Measurements, Recurring | Asset backed – home loans | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Structured Credit | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 29 | |
Fair Value, Measurements, Recurring | Structured Credit | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 29 | |
Fair Value, Measurements, Recurring | Structured Credit | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | | |
Fair Value, Measurements, Recurring | Structured Credit | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | |
Fair Value, Measurements, Recurring | Contract with insurance company | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 11,114 | 19,130 |
Fair Value, Measurements, Recurring | Contract with insurance company | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Contract with insurance company | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Fair Value, Measurements, Recurring | Contract with insurance company | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | $ 11,114 | 19,130 |
Fair Value, Measurements, Recurring | Other | Fair Value, Inputs, Level 1, 2 and 3 | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | | 3 |
Fair Value, Measurements, Recurring | Other | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | | 0 |
Fair Value, Measurements, Recurring | Other | Significant Observable Inputs (Level 2) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | | 0 |
Fair Value, Measurements, Recurring | Other | Significant Unobservable Inputs (Level 3) | | |
Schedule Of Pension Plan Assets By Fair Value [Line Items] | | |
Fair value of plan assets | | $ 3 |