Warrant Liability	3 Months Ended
Mar. 31, 2018
Text Block [Abstract]
Warrant Liability	On December 9, 2016, Shengxin (Shanghai) Management Consulting Limited Partnership (“SMC”), a related party (note 11), delivered RMB 20,124 (approximately $2,981 as of the close of business on such date) in cash (the “SMC Investment”) to ACM Shanghai for potential investment pursuant to terms to be subsequently negotiated On March 14, 2017, ACM, ACM Shanghai and SMC entered into a securities purchase agreement (the “SMC Agreement”) pursuant to which, in exchange for the SMC Investment, ACM issued to SMC a warrant exercisable, for cash or on a cashless basis, to purchase, at any time on or before May 17, 2023, all, but not less than all, of 397,502 shares of Class A common stock at a price of $7.50 per share. The warrant issued to SMC, while outstanding as of December 31, 2017, was classified as a liability as the warrant was conditional puttable in accordance with FASB ASC 480, Distinguishing Liabilities from Equity. The fair value of the warrant was adjusted for changes in fair value at each reporting period but could not be lower than the proceeds of the SMC Investment. The corresponding non-cash gain or loss of the changes in fair value was recorded in earnings. The methodology used to value the warrant was the Black-Scholes valuation model. On March 30, 2018, ACM entered into a warrant exercise agreement with ACM Shanghai and SMC pursuant to which SMC exercised its warrant in full by issuing to ACM a senior secured promissory note in the principal amount of approximately $3,000. ACM then transferred the SMC note to ACM Shanghai in exchange for an intercompany promissory note of ACM Shanghai in the principal amount of approximately $3,000. Each of the two notes bears interest at a rate of 3.01% per annum and matures on August 17, 2023. As security for its performance of its obligations under its note, SMC granted to ACM Shanghai a security interest in the 397,502 shares of Class A common stock issued to SMC upon its exercise of the warrant.

Warrant Liability

3 Months Ended

Mar. 31, 2018

On December 9, 2016, Shengxin (Shanghai) Management Consulting Limited Partnership (“SMC”), a related party (note 11), delivered RMB 20,124 (approximately $2,981 as of the close of business on such date) in cash (the “SMC Investment”) to ACM Shanghai for potential investment pursuant to terms to be subsequently negotiated

On March 14, 2017, ACM, ACM Shanghai and SMC entered into a securities purchase agreement (the “SMC Agreement”) pursuant to which, in exchange for the SMC Investment, ACM issued to SMC a warrant exercisable, for cash or on a cashless basis, to purchase, at any time on or before May 17, 2023, all, but not less than all, of 397,502 shares of Class A common stock at a price of $7.50 per share.

The warrant issued to SMC, while outstanding as of December 31, 2017, was classified as a liability as the warrant was conditional puttable in accordance with FASB ASC 480, Distinguishing Liabilities from Equity. The fair value of the warrant was adjusted for changes in fair value at each reporting period but could not be lower than the proceeds of the SMC Investment. The corresponding non-cash gain or loss of the changes in fair value was recorded in earnings. The methodology used to value the warrant was the Black-Scholes valuation model.

On March 30, 2018, ACM entered into a warrant exercise agreement with ACM Shanghai and SMC pursuant to which SMC exercised its warrant in full by issuing to ACM a senior secured promissory note in the principal amount of approximately $3,000. ACM then transferred the SMC note to ACM Shanghai in exchange for an intercompany promissory note of ACM Shanghai in the principal amount of approximately $3,000. Each of the two notes bears interest at a rate of 3.01% per annum and matures on August 17, 2023. As security for its performance of its obligations under its note, SMC granted to ACM Shanghai a security interest in the 397,502 shares of Class A common stock issued to SMC upon its exercise of the warrant.