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Employee Benefit Plans - Narrative (Detail) | 12 Months Ended
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Dec. 31, 2019 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2019 USD ($) year | Dec. 31, 2019 USD ($) SERP_retirement_age | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Retirement Benefits [Abstract] |  |  |  |  |  |  |
Employers matching contribution |  | 50.00% |  |  |  |  |
Employees first contribution |  | 6.00% |  |  |  |  |
401(k) profit sharing plan, employers matching contribution amount |  |  |  |  | $ 2,200,000 | $ 2,100,000 | $ 1,900,000
SERP annual retirement benefits period (years) | 15 years |  |  |  |  |  |
SERP retirement age |  |  | 65 | 65 |  |  |
SERP target annual retirement benefit | $ 300,000 | $ 300,000 | $ 300,000 | $ 300,000 | 300,000 |  |
SERP annual rate of return |  | 7.00% |  |  |  |  |
SERP present value of the amount owed | $ 5,500,000 | $ 5,500,000 | $ 5,500,000 | $ 5,500,000 | $ 5,500,000 | $ 4,300,000 |

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