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SHARE BASED COMPENSATION - Restricted stock activity (Details) |  | 12 Months Ended
--- | --- | ---
Nov. 22, 2018 $ / shares | Dec. 31, 2020 ¥ / shares shares | Dec. 31, 2019 ¥ / shares shares | Dec. 31, 2018 ¥ / shares shares
Grant-date fair value |  |  |  |
Fair value (per share) | $ / shares | $ 2.70 |  |  |
Restricted stock [Member] |  |  |  |
Shares |  |  |  |
Outstanding at beginning of year (in shares) | shares |  | 171,409 | 273,319 |
Issued (in shares) | shares |  | (50,001) | (101,910) |
Outstanding at end of year (in shares) | shares |  | 121,408 | 171,409 | 273,319
Shares vested but not issued at end of year (in shares) | shares |  | 19,935 | 19,935 |
Grant-date fair value |  |  |  |
Outstanding at beginning of year | ¥ / shares |  | ¥ 19.16 | ¥ 19.31 |
Issued | ¥ / shares |  | 17.62 | 20.20 |
Outstanding at end of year | ¥ / shares |  | 18.10 | 19.16 | ¥ 19.31
Shares vested but not issued at end of year | ¥ / shares |  | ¥ 20.42 | ¥ 21.78 |
Weighted Average Remaining Contractual Term |  |  |  |
Outstanding at beginning of year |  | 1 year 6 months 26 days | 2 years 6 months 18 days | 3 years 4 days
Outstanding at end of year |  | 1 year 6 months 26 days | 2 years 6 months 18 days | 3 years 4 days

X
- Definition The number of equity-based payment instruments, excluding stock (or unit) options that are exercised during the reporting period. + References No definition available. + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options that are vested and expected to vest as of the balance sheet date. + References No definition available. + Details
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- Definition The weighted average fair value of awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan), which are vested or expected to vest as of the balance sheet date. + References No definition available. + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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