RECEIVABLES - Narrative (Details) - USD ($)  | 
6 Months Ended | 12 Months Ended | 
|---|---|---|
Jun. 30, 2021  | 
Dec. 31, 2020  | 
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| Receivables [Abstract] | ||
| Allowance for doubtful accounts | $ 0 | $ 0 | 
| Notes Receivable | ||
| Concentration Risk [Line Items] | ||
| Maximum amount of loss | 5,100,000 | |
| Loss recorded | $ 3,000,000.0 | |
| Customer concentration | Total receivables | Apple, Inc. | ||
| Concentration Risk [Line Items] | ||
| Concentration percentage | 57.80% | 48.90% | 
| Customer concentration | Total receivables | Google, Inc. | ||
| Concentration Risk [Line Items] | ||
| Concentration percentage | 26.30% | 42.70% | 
| Customer concentration | Total notes receivable | Notes Receivable | ||
| Concentration Risk [Line Items] | ||
| Concentration percentage | 93.50% | |
| Customer concentration | Total notes receivable | Notes Receivable | Certain intellectual property created, developed or acquired by the developers | ||
| Concentration Risk [Line Items] | ||
| Concentration percentage | 40.00% | 
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- Definition Amount of allowance for credit loss on accounts receivable, classified as current. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of allowance for credit loss on financing receivable, classified as noncurrent. 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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- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Reflects the estimated amount of loss from the specified contingency as of the balance sheet date. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- References No definition available. 
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