SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Reconciliation of net income (loss) per share (Details) - USD ($)			3 Months Ended		6 Months Ended		9 Months Ended
		Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2018
Reconciliation of net income (loss) per share
Net income (loss)			$ (3,852,738)	$ 610,435	$ 608,749		$ (4,497,788)
Less: Income attributable to ordinary shares subject to redemption		$ 0	(1,314,381)	0		$ 0	(4,122,975)
Adjusted net income (loss)			$ (5,167,119)	$ 610,435	$ 608,749		$ (8,620,763)
Weighted average shares outstanding, basic and diluted	[1]		13,406,386	12,303,095	11,190,364		13,244,997
Basic and diluted net income (loss) per common share	[2]		$ (0.39)	$ 0.05	$ 0.05		$ (0.65)

[1] September 30, 2018 and 2017 excludes an aggregate of 43,513,414 and 44,341,965 shares subject to possible redemption.

[2] Net income (loss) per common share — basic and diluted excludes income attributable to common stock subject to possible redemption of $1,314,381 and $4,122,975 for the three and nine months ended September 30, 2018, respectively, and $0 for the three and nine months ended September 30, 2017 (see Note 3).