Segment Information - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information
Total revenue	$ 77,246	$ 52,207	$ 149,541	$ 122,479
Total Real Estate
Segment Reporting Information
Total revenue	56,291	38,371	107,445	88,276
Mortgage
Segment Reporting Information
Total revenue	2,410	1,070	4,733	2,528
Marketing Funds fees
Segment Reporting Information
Total revenue	18,042	11,765	36,187	29,287
Other
Segment Reporting Information
Total revenue	503	1,001	1,176	2,388
Continuing franchise fees
Segment Reporting Information
Total revenue	26,955	16,738	52,329	40,881
Continuing franchise fees | Total Real Estate
Segment Reporting Information
Total revenue	25,039	15,795	48,648	38,672
Continuing franchise fees | Mortgage
Segment Reporting Information
Total revenue	1,916	943	3,681	2,209
Annual dues
Segment Reporting Information
Total revenue	8,869	8,745	17,541	17,666
Annual dues | Total Real Estate
Segment Reporting Information
Total revenue	8,869	8,745	17,541	17,666
Broker fees
Segment Reporting Information
Total revenue	17,453	10,426	29,406	19,870
Broker fees | Total Real Estate
Segment Reporting Information
Total revenue	17,453	10,426	29,406	19,870
Franchise sales and other revenue
Segment Reporting Information
Total revenue	5,927	4,533	14,078	14,775
Franchise sales and other revenue | Total Real Estate
Segment Reporting Information
Total revenue	4,930	3,405	11,850	12,068
Franchise sales and other revenue | Mortgage
Segment Reporting Information
Total revenue	$ 494	$ 127	$ 1,052	$ 319