Retirement Plans - Schedule of Weighted-Average Assumptions Used to Determine Net Periodic Cost (Detail) - Net Periodic Cost [Member] |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
Net Periodic Benefit Cost Assumptions [Line Items] | |||
Discount rate | 4.11% | 3.37% | 3.74% |
Health care cost trend: Initial | 6.00% | 6.00% | 6.00% |
Health care cost trend: Ultimate | 4.75% | 4.75% | 4.75% |
Year ultimate reached | 2024 | 2023 | 2022 |
Corridor | 10.00% | 10.00% | 10.00% |
Recognition period for gains and losses | 12 years 1 month 6 days | 12 years 1 month 6 days | 11 years |