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Retirement Plans and Other Postretirement Benefits - Fair Value of Plan Assets (Detail) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets $ 913,034 $ 845,979
U.S. Defined Benefit Pension Plans    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 662,298 621,632
U.S. Defined Benefit Pension Plans | Municipal bonds    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 876 574
U.S. Defined Benefit Pension Plans | Corporate debt instruments    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 3,442 3,152
U.S. Defined Benefit Pension Plans | Corporate debt instruments – Preferred    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 12,196 10,781
U.S. Defined Benefit Pension Plans | Corporate stocks – Common    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 62,897 127,221
U.S. Defined Benefit Pension Plans | U.S. Government securities    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 526 240
U.S. Defined Benefit Pension Plans | Total investments    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 316,467 430,044
U.S. Defined Benefit Pension Plans | Investments measured at net asset value    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 345,831 191,588
U.S. Defined Benefit Pension Plans | Registered investment companies    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 236,530 288,076
Level 1 | U.S. Defined Benefit Pension Plans    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 299,427 415,297
Level 1 | U.S. Defined Benefit Pension Plans | Corporate stocks – Common    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 62,897 127,221
Level 1 | U.S. Defined Benefit Pension Plans | U.S. Government securities    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 0  
Level 1 | U.S. Defined Benefit Pension Plans | Total investments    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 299,427 415,297
Level 1 | U.S. Defined Benefit Pension Plans | Registered investment companies    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 236,530 288,076
Level 2 | U.S. Defined Benefit Pension Plans    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 17,040 14,747
Level 2 | U.S. Defined Benefit Pension Plans | Municipal bonds    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 876 574
Level 2 | U.S. Defined Benefit Pension Plans | Corporate debt instruments    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 3,442 3,152
Level 2 | U.S. Defined Benefit Pension Plans | Corporate debt instruments – Preferred    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 12,196 10,781
Level 2 | U.S. Defined Benefit Pension Plans | U.S. Government securities    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 526 240
Level 2 | U.S. Defined Benefit Pension Plans | Total investments    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets 17,040 $ 14,747
Level 2 | U.S. Defined Benefit Pension Plans | Registered investment companies    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets $ 0