Summary of Significant Accounting Policies - Retirement Benefits (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
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| Summary of Significant Accounting Policies | |||
| Pension contributions | $ 2,070,000 | $ 1,904,000 | $ 1,847,000 |
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- References No definition available.
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- Definition Amount of cost for defined contribution plan. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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