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, 2018 |
Mar. 31, 2017 |
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| Balance Sheet Related Disclosures [Abstract] | ||
| Increase in the carrying value of the assets held in the rabbi trust | $ 14 | $ 199 |
| Increase in the carrying value of the deferred compensation obligation | $ 0 | $ 211 |
| X | ||||||||||
- 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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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- 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://www.xbrl.org/2003/role/presentationRef
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