Fair value measurement - Fair Value of Pension Plan Assets by Level within Fair Value Hierarchy (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	$ 541,758
Retirement Plans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	541,758	$ 552,996	$ 479,735
Retirement Plans | Fair Value, Inputs, Level 1, 2 and 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	32,107	181,398
Retirement Plans | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	32,107	181,398
Retirement Plans | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	0	0
Retirement Plans | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	0	0
Retirement Plans | Cash and other | Fair Value, Inputs, Level 1, 2 and 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	544	1,310
Retirement Plans | Cash and other | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	544	1,310
Retirement Plans | Cash and other | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	0	0
Retirement Plans | Cash and other | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	0	0
Retirement Plans | Corporate stock | Fair Value, Inputs, Level 1, 2 and 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	25,324	109,088
Retirement Plans | Corporate stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	25,324	109,088
Retirement Plans | Corporate stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	0	0
Retirement Plans | Corporate stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	0	0
Retirement Plans | Interest in registered investment companies | Fair Value, Inputs, Level 1, 2 and 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	6,239	71,000
Retirement Plans | Interest in registered investment companies | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	6,239	71,000
Retirement Plans | Interest in registered investment companies | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	0	0
Retirement Plans | Interest in registered investment companies | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	0	0
Retirement Plans | Common collective trust - equities | Fair Value Measured at Net Asset Value Per Share
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	22,356	96,447
Retirement Plans | Common collective trust - fixed income | Fair Value Measured at Net Asset Value Per Share
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	465,842	252,426
Retirement Plans | Hedge fund | Fair Value Measured at Net Asset Value Per Share
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	19,156	18,033
Retirement Plans | Partnership/joint venture interests | Fair Value Measured at Net Asset Value Per Share
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value of plan assets	$ 2,297	$ 4,692