Segment Reporting and Revenue - Reconciliation of Operating Profit (Loss) from Segments to Consolidated (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	$ 886,093	$ 779,796	$ 486,920
Cost of revenue	653,983	635,693	367,496
Gross profit	232,110	144,103	119,424
Operating expenses	231,318	223,349	163,358
Interest income	2,074	7,146	5,416
Interest expense	(19,495)	(8,928)	(3,681)
Net loss	(18,527)	(80,805)	(41,978)
Operating Segments | Real estate services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	651,208	523,540	432,168
Cost of revenue	417,140	373,150	309,069
Gross profit	234,068	150,390	123,099
Operating Segments | Real estate services | Brokerage revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	607,513	496,480	406,293
Operating Segments | Real estate services | Partner revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	43,695	27,060	25,875
Operating Segments | Properties
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	209,686	240,507	44,993
Cost of revenue	214,382	245,189	46,613
Gross profit	(4,696)	(4,682)	(1,620)
Operating Segments | Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	28,212	17,634	9,882
Cost of revenue	25,474	19,239	11,937
Gross profit	2,738	(1,605)	(2,055)
Intercompany eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	(3,013)	(1,885)	(123)
Cost of revenue	(3,013)	(1,885)	(123)
Gross profit	$ 0	$ 0	$ 0