GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Goodwill (Detail) $ in Thousands		6 Months Ended
	Apr. 12, 2018 USD ($)	Jun. 30, 2018 USD ($) period segment	Jun. 30, 2017 USD ($)
Goodwill activity
Beginning balance		$ 123,767	$ 96,420
Additions from acquisitions		29,957	27,347
Ending balance		$ 153,724	123,767
Assets acquired
Business acquisition date	Apr. 12, 2018
Number of Reporting Units | segment		1
Contingent liability
Payment of contingent consideration		$ 5,150	0
Number of annual contingent consideration earn-out periods | period		3
Contingent consideration		$ 9,400	$ 14,100
JCR
Goodwill activity
Additions from acquisitions	$ 30,000
Assets acquired
Ownership interest acquired	100.00%
Purchase consideration paid in cash	$ 35,000
Goodwill, tax deductible portion	0
Intangible assets acquired		$ 2,800
Amortization period of intangible assets		5 years
JCR | Level 2
Assets acquired
Accounts receivable	4,200
JCR | Registered investment advisor license | Level 3
Assets acquired
Intangible assets acquired	$ 2,400