| Reportable Segments - Assets by Geography (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019 | 
|---|---|---|
| Revenues from External Customers and Long-Lived Assets | ||
| Long-lived assets | $ 1,031,474 | $ 1,059,573 | 
| United States | ||
| Revenues from External Customers and Long-Lived Assets | ||
| Long-lived assets | 749,635 | 784,699 | 
| Netherlands | ||
| Revenues from External Customers and Long-Lived Assets | ||
| Long-lived assets | 53,006 | 49,559 | 
| United Kingdom | ||
| Revenues from External Customers and Long-Lived Assets | ||
| Long-lived assets | 100,392 | 92,229 | 
| Other foreign countries | ||
| Revenues from External Customers and Long-Lived Assets | ||
| Long-lived assets | $ 128,441 | $ 133,086 | 
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- Definition Long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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