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Employee Savings Plan - Additional Information (Detail) - USD ($) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Retirement Benefits [Abstract] |  |  |
Minimum age to be eligible to defined contribution plan | 21 years |  |
Maximum contribution by company expressed as percentage of employee pre-tax salary | 100.00% |  |
Company match percent | 50.00% |  |
Percent of employee contribution | 6.00% |  |
Company contributions vest at end of one year | 25.00% |  |
Company contributions vest at end of two years | 50.00% |  |
Company contributions vest at end of three years | 75.00% |  |
Company contributions vest at end of four years | 100.00% |  |
Company contributions to employee savings plan | $ 2,636,000 | $ 2,729,000 | $ 2,540,000

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- Definition Minimum age to be eligible to defined contribution plan. + References No definition available. + Details
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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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