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FAIR VALUE MEASUREMENTS - Narrative (Detail) - USD ($) $ in Thousands |  | 2 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | ---
Oct. 01, 2018 | Nov. 23, 2018 | Sep. 30, 2020 | Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2019 | Jul. 20, 2018
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |
Purchase of additional Sangamo France shares |  |  |  | $ 503 | $ 262 |  |  |
Sangamo France |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |
Number of shares acquired (in shares) | 13,519,036 | 11,528,635 |  |  |  |  |  |
Sangamo France | Share Purchase Agreement and Tender Offer Agreement |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |
Number of free shares held by the holders (in shares) |  |  |  |  |  |  |  | 477,000
Estimated fair value liability of free shares |  |  |  |  |  |  | $ 200 | $ 200
Number of shares acquired (in shares) |  |  |  | 228,000 |  | 25,047,671 | 111,000 |
Purchase of additional Sangamo France shares |  |  |  | $ 500 |  |  | $ 300 |
Number of free shares outstanding subject to purchase (in shares) |  |  | 138,000 |  |  |  |  |
Value of shares repurchased |  |  |  | $ 100 |  |  |  |

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