Segment Reporting and Revenue - Reconciliation of Operating Profit (Loss) from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	$ 238,683	$ 140,255	$ 546,605	$ 362,791
Cost of revenue	185,306	97,950	442,127	269,576
Gross profit	53,377	42,305	104,478	93,215
Operating expenses	45,941	39,016	176,913	124,643
Interest income	1,576	1,775	5,804	3,082
Interest expense	(2,274)	(1,610)	(6,564)	(1,610)
Other income, net	44	21	172	200
Net income (loss)	6,782	3,475	(73,023)	(29,756)
Operating Segments \| Real estate services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	154,126	126,265	392,862	332,047
Cost of revenue	100,048	83,274	284,447	236,775
Gross profit	54,078	42,991	108,415	95,272
Operating Segments \| Properties
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	80,164	11,350	141,445	23,388
Cost of revenue	80,909	11,656	144,807	24,086
Gross profit	(745)	(306)	(3,362)	(698)
Other revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	5,161	2,691	13,490	7,407
Cost of revenue	5,117	3,071	14,065	8,766
Gross profit	44	(380)	(575)	(1,359)
Intercompany eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Cost of revenue	(768)	(51)	(1,192)	(51)
Gross profit	0	0	0	0
Brokerage revenue \| Operating Segments \| Real estate services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	146,096	118,809	372,809	312,306
Partner revenue \| Operating Segments \| Real estate services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	$ 8,030	$ 7,456	$ 20,053	$ 19,741

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