Segment Information - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information
Total revenue	$ 72,295	$ 70,272
Total Real Estate
Segment Reporting Information
Total revenue	51,154	49,905
Mortgage
Segment Reporting Information
Total revenue	2,323	1,458
Marketing Funds fees
Segment Reporting Information
Total revenue	18,145	17,522
Other
Segment Reporting Information
Total revenue	673	1,387
Continuing franchise fees
Segment Reporting Information
Total revenue	25,374	24,143
Continuing franchise fees | Total Real Estate
Segment Reporting Information
Total revenue	23,609	22,877
Continuing franchise fees | Mortgage
Segment Reporting Information
Total revenue	1,765	1,266
Annual dues
Segment Reporting Information
Total revenue	8,672	8,921
Annual dues | Total Real Estate
Segment Reporting Information
Total revenue	8,672	8,921
Broker fees
Segment Reporting Information
Total revenue	11,953	9,444
Broker fees | Total Real Estate
Segment Reporting Information
Total revenue	11,953	9,444
Franchise sales and other revenue
Segment Reporting Information
Total revenue	8,151	10,242
Franchise sales and other revenue | Total Real Estate
Segment Reporting Information
Total revenue	6,920	8,663
Franchise sales and other revenue | Mortgage
Segment Reporting Information
Total revenue	$ 558	$ 192