Retirement Plans - Summary of Plan's Weighted Average Asset Allocations (Detail) |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total weighted average asset | 100.00% | 100.00% |
| Equity Securities [Member] | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total weighted average asset | 63.00% | 61.00% |
| Debt Securities [Member] | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total weighted average asset | 30.00% | 32.00% |
| Real Estate [Member] | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total weighted average asset | 7.00% | 7.00% |