6. Goodwill and Indefinite-Lived Intangible Assets and Other Long-Term Assets (Tables)  | 
12 Months Ended | |||||||||||||||||||||||||
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Dec. 31, 2019  | ||||||||||||||||||||||||||
| Goodwill and Intangible Assets Disclosure [Abstract] | ||||||||||||||||||||||||||
| Reconciliation of Change in Carrying Value of Goodwill | 
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| X | ||||||||||
- References No definition available. 
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- Definition Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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