Segment Information - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information
Total revenue	$ 90,997	$ 71,073	$ 240,538	$ 193,552
Total Real Estate
Segment Reporting Information
Total revenue	64,623	50,952	172,068	139,228
Mortgage
Segment Reporting Information
Total revenue	2,620	1,906	7,353	4,434
Marketing Funds fees
Segment Reporting Information
Total revenue	23,269	17,290	59,456	46,577
Other
Segment Reporting Information
Total revenue	485	925	1,661	3,313
Continuing franchise fees
Segment Reporting Information
Total revenue	32,464	24,339	84,793	65,220
Continuing franchise fees | Total Real Estate
Segment Reporting Information
Total revenue	30,416	22,799	79,064	61,471
Continuing franchise fees | Mortgage
Segment Reporting Information
Total revenue	2,048	1,540	5,729	3,749
Annual dues
Segment Reporting Information
Total revenue	8,967	8,638	26,508	26,304
Annual dues | Total Real Estate
Segment Reporting Information
Total revenue	8,967	8,638	26,508	26,304
Broker fees
Segment Reporting Information
Total revenue	19,245	15,457	48,651	35,327
Broker fees | Total Real Estate
Segment Reporting Information
Total revenue	19,245	15,457	48,651	35,327
Franchise sales and other revenue
Segment Reporting Information
Total revenue	7,052	5,349	21,130	20,124
Franchise sales and other revenue | Total Real Estate
Segment Reporting Information
Total revenue	5,995	4,058	17,845	16,126
Franchise sales and other revenue | Mortgage
Segment Reporting Information
Total revenue	$ 572	$ 366	$ 1,624	$ 685