RELATED PARTY TRANSACTIONS (Details) - USD ($)				3 Months Ended	6 Months Ended
	Jun. 19, 2017	Apr. 04, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2017	Jul. 24, 2017
Related Party Loans
Exercise price of warrants (in dollars per share)				$ 1.00	$ 1.00	$ 1.00
Initial Stockholders
Founder Shares
Percentage of shares held by related party				0.20%	0.20%	0.20%
Holding period of founder shares					1 year
Affiliate of Sponsor | Administrative Support Agreement
Administrative Support Agreement
Monthly service fees					$ 10,000
Service fees incurred			$ 30,000	$ 30,000		$ 30,000
Maximum
Related Party Loans
Conversion of working capital loan to warrants					$ 2,000,000
Class A Common Stock
Founder Shares
Aggregated shares issued				1,658,035	1,658,035	1,658,035
Common stock, par value				$ 0.0001	$ 0.0001	$ 0.0001
Related Party Loans
Exercise price of warrants (in dollars per share)							$ 11.50
Number of warrants issued in exchange for working capital loan					2,000,000
Class A Common Stock | Initial Stockholders
Founder Shares
Stock price threshold that allows transfer of shares				$ 12.00	$ 12.00	$ 12.00
Number of trading days within 30 days required for the transfer, assignment or sale of shares					20 days
Period over which the required trading days of shares at $12.00 per share or over had to occur					30 days
Minimum period after initial business combination to allow transfer of founders shares					150 days
Class F Common Stock
Founder Shares
Aggregated shares issued	11,500,000			11,500,000	11,500,000	11,500,000
Common stock, par value				$ 0.0001	$ 0.0001	$ 0.0001
Founder Shares Maximum Number of Shares Subject to Forfeiture to Maintain Percentage of Issued and Outstanding Shares Held by Initial Stockholders				1,500,000	1,500,000	1,500,000
Class F Common Stock | Federal Street Sponsor LLC
Founder Shares
Aggregated shares issued		10,062,500
Stock dividend shares	1,437,500
Proceeds from issuance of common stock		$ 25,000
Founder shares aggregate (in shares)					1,500,000
IPO | Federal Street Sponsor LLC | Promissory Note
Related Party Loans
Maximum borrowing capacity				$ 250,000	$ 250,000	$ 250,000