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COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands |  |  | 12 Months Ended
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Aug. 27, 2018 USD ($) | Aug. 27, 2018 CNY (¥) | Jul. 09, 2018 CNY (¥) | Dec. 31, 2018 USD ($) Defendant | Dec. 31, 2018 EUR (€) Defendant | Dec. 31, 2018 CNY (¥) Defendant | Dec. 31, 2017 USD ($) | Dec. 31, 2015 Subsidiary
Future minimum lease payments for operating leases [Abstract] |  |  |  |  |  |  |  |
2019 |  |  |  | $ 7,363 |  |  |  |
2020 |  |  |  | 6,017 |  |  |  |
2021 |  |  |  | 4,967 |  |  |  |
2022 |  |  |  | 3,338 |  |  |  |
2023 |  |  |  | 1,194 |  |  |  |
Thereafter |  |  |  | 442 |  |  |  |
Total future minimum lease payments for operating leases |  |  |  | 23,321 |  |  |  |
Rent expense for leases |  |  |  | 8,000 |  |  | $ 8,200 |
Other commitments [Abstract] |  |  |  |  |  |  |  |
Outstanding purchase orders related to raw materials |  |  |  | 58,900 |  |  | 45,400 |
Outstanding purchase orders related to capital expenditures |  |  |  | 5,200 |  |  | $ 3,000 |
Dongguan Transpower [Member] |  |  |  |  |  |  |  |
Loss Contingency, Estimate [Abstract] |  |  |  |  |  |  |  |
Damages received with incurred interest | $ 3,200 | ¥ 20,430,203 |  |  |  |  |  |
Arezzo Revenue Agency [Member] |  |  |  |  |  |  |  |
Loss Contingency, Estimate [Abstract] |  |  |  |  |  |  |  |
Estimated liability |  |  |  | $ 12,000 |  |  |  |
Setec [Member] |  |  |  |  |  |  |  |
Loss Contingency, Estimate [Abstract] |  |  |  |  |  |  |  |
Number of subsidiaries named in the lawsuit | Subsidiary |  |  |  |  |  |  |  | 3
Setec [Member] | Dongguan Transpower [Member] |  |  |  |  |  |  |  |
Loss Contingency, Estimate [Abstract] |  |  |  |  |  |  |  |
Amount paid in exchange for perpetual, worldwide royalty-free license to patent-in-suit | € |  |  |  |  | € 75,000 |  |  |
DG Yu Shing Industrial Development Company Limited [Member] | Dongguan Transpower [Member] |  |  |  |  |  |  |  |
Loss Contingency, Estimate [Abstract] |  |  |  |  |  |  |  |
Number of defendants | Defendant |  |  |  | 3 | 3 | 3 |  |
Damages sought |  |  |  | $ 3,200 |  |  |  |
Damages awarded | ¥ |  |  |  |  |  | ¥ 20,133,174.10 |  |
Jinmei Entities [Member] |  |  |  |  |  |  |  |
Loss Contingency, Estimate [Abstract] |  |  |  |  |  |  |  |
Damages received with incurred interest | ¥ |  |  | ¥ 20,133,174 |  |  |  |  |

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