The discount percentage of purchase price paid by employee entities.

No definition available.

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- Definition

Weighted average grant-date fair value of non-vested options exercised.

+ References

No definition available.

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- Definition

Weighted average grant-date fair value of non-vested options expired.

+ References

No definition available.

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- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

+ References

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- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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- References

No definition available.

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- Definition

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

+ References

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- Definition

Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

+ References

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- Definition

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

+ References

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- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

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- Definition

Number of options outstanding, including both vested and non-vested options.

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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.

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ References

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- References

No definition available.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

+ References

No definition available.

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- Definition

Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

+ References

No definition available.

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- Definition

Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

+ References

No definition available.

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

+ References

No definition available.

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- Definition

Weighted average grant-date fair value of non-vested options forfeited.

+ References

No definition available.

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- Definition

Weighted average grant-date fair value of non-vested options outstanding.

+ References

No definition available.

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- Definition

Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

Number of share options (or share units) exercised during the current period.

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STOCK-BASED COMPENSATION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
ACM Shanghai [Member]
Weighed Average Remaining Contractual Term [Abstract]
Percentage of discount on purchase price for employee entities	20.00%
Employee Share Option [Member]
Number of Option Share [Roll Forward]
Outstanding, beginning of period (in shares)			2,503,405
Granted (in shares)	319,000		614,000
Exercised (in shares)			(105,113)
Expired (in shares)			(628)
Forfeited/cancelled (in shares)			(41,203)
Outstanding, end of period (in shares)	2,970,461		2,970,461		2,503,405
Vested and exercisable (in shares)	1,673,780		1,673,780
Weighted Average Grant Date Fair Value [Abstract]
Outstanding at beginning of period (in dollars per share)			$ 0.91
Granted (in dollars per share)			6.30
Exercised (in dollars per share)			0.60
Expired (in dollars per share)			0.55
Forfeited/cancelled (in dollars per share)			1.35
Outstanding at end of period (in dollars per share)	$ 2.55		2.55		$ 0.91
Weighted Average Exercise Price [Abstract]
Outstanding, beginning of period (in dollars per share)			4.09
Granted (in dollars per share)			16.39
Exercised (in dollars per share)			2.08
Expired (in dollars per share)			3.00
Forfeited/cancelled (in dollars per share)			3.82
Outstanding, end of period (in dollars per share)	$ 6.71		$ 6.71		$ 4.09
Weighed Average Remaining Contractual Term [Abstract]
Outstanding weighed average remaining contractual term			7 years 3 months 11 days		7 years 3 months 18 days
Stock-based compensation expense	$ 1,329	$ 195	$ 1,841	$ 458
Unrecognized employee stock-based compensation expense	$ 5,009		$ 5,009		$ 2,424
Weighted-average period over which unrecognized compensation is expected to be recognized			1 year 7 months 17 days		1 year 7 months 13 days
Employee Share Option [Member] \| Class A Common Stock [Member]
Number of Option Share [Roll Forward]
Forfeited/cancelled (in shares)	(31,339)		(31,339)
Employee Share Option [Member] \| ACM Shanghai [Member]
Weighed Average Remaining Contractual Term [Abstract]
Percentage of discount on purchase price for employee entities			20.00%
Stock-based compensation expense			$ 949
Non-Employee Share Option [Member]
Number of Option Share [Roll Forward]
Outstanding, beginning of period (in shares)			1,212,374
Granted (in shares)			0
Exercised (in shares)			(88,529)
Expired (in shares)			0
Forfeited/cancelled (in shares)			(22,232)
Outstanding, end of period (in shares)	1,101,613		1,101,613		1,212,374
Vested and exercisable (in shares)	959,845		959,845
Weighted Average Grant Date Fair Value [Abstract]
Outstanding at beginning of period (in dollars per share)			$ 0.78
Granted (in dollars per share)			0
Exercised (in dollars per share)			0.45
Expired (in dollars per share)			0
Forfeited/cancelled (in dollars per share)			0.55
Outstanding at end of period (in dollars per share)	$ 0.82		0.82		$ 0.78
Weighted Average Exercise Price [Abstract]
Outstanding, beginning of period (in dollars per share)			2.57
Granted (in dollars per share)			0
Exercised (in dollars per share)			1.06
Expired (in dollars per share)			0
Forfeited/cancelled (in dollars per share)			3.00
Outstanding, end of period (in dollars per share)	$ 2.69		$ 2.69		$ 2.57
Weighed Average Remaining Contractual Term [Abstract]
Outstanding weighed average remaining contractual term			6 years 1 month 6 days		6 years 7 months 28 days
Stock-based compensation expense	$ 228	$ 216	$ 1,078	$ 2,313
Unrecognized employee stock-based compensation expense	$ 634		$ 634		$ 1,713
Weighted-average period over which unrecognized compensation is expected to be recognized			3 months 29 days		1 year 3 months 22 days
Non-Employee Share Option [Member] \| Class A Common Stock [Member] \| Director [Member]
Number of Option Share [Roll Forward]
Forfeited/cancelled (in shares)	(22,232)		(22,232)