IPO, REORGANIZATION TRANSACTIONS AND USE OF PROCEEDS (Details) $ / shares in Units, $ in Thousands		1 Months Ended
	Jul. 30, 2018 USD ($) Vote $ / shares shares	Mar. 31, 2019 $ / shares shares	Dec. 31, 2018 $ / shares
Class A common stock
Initial Public Offering
Issuance of stock (in shares)		403,712
Common stock, par value | $ / shares		$ 0.01	$ 0.01
Reorganization Transactions
Number of votes for each share | Vote	1
Issue of shares, Reorganization transaction	23,881,002
Non-compensatory stock options issued to purchase of common stock under the reorganization transaction	386,832
Compensatory stock options issued to purchase of common stock under the reorganization transaction	348,577
Number of shares cancelled under reorganization transaction	240,457
Class B common stock
Initial Public Offering
Common stock, par value | $ / shares		$ 0.01	$ 0.01
Reorganization Transactions
Number of votes for each share | Vote	1
Issue of shares, Reorganization transaction	22,499,665
Number of new shares issued after cancellation under the reorganization transaction	240,457
IPO
Reorganization Transactions
Net proceeds used to pay certain owners | $	$ 35,537
Number of units exchanged	17,583,947
Repayment of credit facility | $	$ 392,535
Residual contribution | $	137,088
IPO | Focus LLC
Reorganization Transactions
Payment for exchange of units | $	$ 529,623
IPO | Class A common stock
Initial Public Offering
Issuance of stock (in shares)	18,648,649
Common stock, par value | $ / shares	$ 0.01
Reorganization Transactions
Proceeds from sale of common stock | $	$ 565,160
Underwriters option | Class A common stock
Initial Public Offering
Issuance of stock (in shares)	2,432,432
Share price (in dollars per share) | $ / shares	$ 33.00
Reorganization Transactions
Proceeds from sale of common stock | $	$ 74,651