GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Goodwill (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Gross Goodwill
Beginning balance		$ 963,710	$ 959,712
Additions from acquisitions		0	0
Measurement-period adjustments		0	3,998
Ending gross goodwill balance	$ 963,710	963,710	963,710
Accumulated Goodwill Impairment
Beginning balance		62,000
Impairment	14,000	0	14,000
Ending accumulated goodwill impairment	14,000	62,000	14,000
Goodwill	949,710	901,710	949,710	$ 901,710
Capital Markets
Gross Goodwill
Beginning balance		524,189	520,191
Additions from acquisitions		0	0
Measurement-period adjustments		0	3,998
Ending gross goodwill balance	524,189	524,189	524,189
Accumulated Goodwill Impairment
Beginning balance		62,000
Impairment		0	14,000
Ending accumulated goodwill impairment	14,000	62,000	14,000
Goodwill	510,189	462,189	510,189
Servicing and Asset Management
Gross Goodwill
Beginning balance		439,521	439,521
Additions from acquisitions		0	0
Measurement-period adjustments		0	0
Ending gross goodwill balance	439,521	439,521	439,521
Accumulated Goodwill Impairment
Impairment		0	0
Goodwill	439,521	439,521	439,521
Corporate
Accumulated Goodwill Impairment
Goodwill	$ 0	$ 0	$ 0	$ 0	$ 0