Segment Reporting and Revenue - Reconciliation of Operating Profit (Loss) from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Brokerage revenue	$ 110,141	$ 79,893
Cost of revenue	107,388	74,197
Gross profit	2,753	5,696
Operating expenses	70,205	42,870
Interest income	2,316	577
Interest expense	(2,136)	0
Other income, net	92	158
Net loss	(67,180)	(36,439)
Operating Segments | Real estate services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Brokerage revenue	85,890	74,924
Cost of revenue	80,784	68,164
Gross profit	5,106	6,760
Operating Segments | Properties
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Brokerage revenue	21,373	3,052
Cost of revenue	22,993	3,342
Gross profit	(1,620)	(290)
Other revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Brokerage revenue	3,047	1,917
Cost of revenue	3,780	2,691
Gross profit	(733)	(774)
Intercompany eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Brokerage revenue	(169)	0
Cost of revenue	(169)	0
Gross profit	0	0
Brokerage revenue | Operating Segments | Real estate services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Brokerage revenue	81,314	70,143
Partner revenue | Operating Segments | Real estate services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Brokerage revenue	$ 4,576	$ 4,781