REVENUE RECOGNITION - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Total revenue	$ 214,333	$ 253,403
New York City
Disaggregation of Revenue [Line Items]
Total revenue	60,722	83,745
Northeast
Disaggregation of Revenue [Line Items]
Total revenue	39,251	43,365
Southeast
Disaggregation of Revenue [Line Items]
Total revenue	77,586	81,773
West
Disaggregation of Revenue [Line Items]
Total revenue	36,700	44,520
International
Disaggregation of Revenue [Line Items]
Total revenue	74	0
Commission and other brokerage income - existing home sales
Disaggregation of Revenue [Line Items]
Total revenue	197,866	220,007
Commission and other brokerage income - existing home sales \| New York City
Disaggregation of Revenue [Line Items]
Total revenue	51,491	66,217
Commission and other brokerage income - existing home sales \| Northeast
Disaggregation of Revenue [Line Items]
Total revenue	39,251	42,995
Commission and other brokerage income - existing home sales \| Southeast
Disaggregation of Revenue [Line Items]
Total revenue	73,264	69,399
Commission and other brokerage income - existing home sales \| West
Disaggregation of Revenue [Line Items]
Total revenue	33,786	41,396
Commission and other brokerage income - existing home sales \| International
Disaggregation of Revenue [Line Items]
Total revenue	74	0
Commission and other brokerage income - development marketing
Disaggregation of Revenue [Line Items]
Total revenue	14,015	21,136
Commission and other brokerage income - development marketing \| New York City
Disaggregation of Revenue [Line Items]
Total revenue	9,221	8,170
Commission and other brokerage income - development marketing \| Northeast
Disaggregation of Revenue [Line Items]
Total revenue	0	152
Commission and other brokerage income - development marketing \| Southeast
Disaggregation of Revenue [Line Items]
Total revenue	4,321	12,374
Commission and other brokerage income - development marketing \| West
Disaggregation of Revenue [Line Items]
Total revenue	473	440
Commission and other brokerage income - development marketing \| International
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Property management revenue
Disaggregation of Revenue [Line Items]
Total revenue		9,492
Property management revenue \| New York City
Disaggregation of Revenue [Line Items]
Total revenue		9,282
Property management revenue \| Northeast
Disaggregation of Revenue [Line Items]
Total revenue		210
Property management revenue \| Southeast
Disaggregation of Revenue [Line Items]
Total revenue		0
Property management revenue \| West
Disaggregation of Revenue [Line Items]
Total revenue		0
Property management revenue \| International
Disaggregation of Revenue [Line Items]
Total revenue		0
Other ancillary services
Disaggregation of Revenue [Line Items]
Total revenue	2,452	2,768
Other ancillary services \| New York City
Disaggregation of Revenue [Line Items]
Total revenue	10	76
Other ancillary services \| Northeast
Disaggregation of Revenue [Line Items]
Total revenue	0	8
Other ancillary services \| Southeast
Disaggregation of Revenue [Line Items]
Total revenue	1	0
Other ancillary services \| West
Disaggregation of Revenue [Line Items]
Total revenue	2,441	2,684
Other ancillary services \| International
Disaggregation of Revenue [Line Items]
Total revenue	$ 0	$ 0