DIVESTITURES (Details) - USD ($) $ in Thousands			3 Months Ended										12 Months Ended
	Dec. 03, 2018	Apr. 13, 2018	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sales of affiliates													$ 0	$ 0	$ 52,981
Income tax expense/(benefit)			$ 6,124	$ 1,821	$ 841	$ 102	$ 6,788	$ 5,517	$ 5,369	$ 4,917			8,888	22,591	37,537
Gain (loss) on sale of affiliate													0	$ 0	$ 18,142
Bingham, Osborn & Scarborough, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale	$ 21,100
Revenue sharing term	8 years
Proceeds from sales of affiliates	$ 13,900
Contingent consideration receivable			11,800										11,800
Income tax expense/(benefit)											$ 3,500
Gain (loss) on sale of affiliate											$ 18,100
Anchor
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale		$ 31,800
Proceeds from sales of affiliates		15,400
Contingent consideration receivable			$ 9,800										$ 9,800
Income tax expense/(benefit)		12,700
Gain (loss) on sale of affiliate		$ (1,300)
Goodwill impairment charge												$ 24,900
Westfield Capital Management Company
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining ownership percentage												12.50%
Remaining annual maximum revenue												$ 11,600