Selected Balance Sheet Data - Summary of Net Change in Carrying Value of Assets Held in Rabbi Trust and Deferred Compensation Liability (Detail) - USD ($) $ in Thousands  | 
3 Months Ended | |
|---|---|---|
Mar. 31, 2021  | 
Mar. 31, 2020  | 
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| Balance Sheet Related Disclosures [Abstract] | ||
| Increase (decrease) in the carrying value of the assets held in the rabbi trust | $ 333 | $ (1,388) | 
| Increase (decrease) in the net carrying value of the deferred compensation obligation | $ 260 | $ (1,273) | 
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- Definition The amount of increase or decrease in the fair value of plan assets during the reporting period. No definition available. 
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- References No definition available. 
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- Definition The increase (decrease) during the reporting period in the obligation created by employee agreements whereby earned compensation will be paid in the future. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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