Segment Information - Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information
Total revenue	$ 266,001	$ 282,293	$ 212,626
Real Estate
Segment Reporting Information
Total revenue	190,792	199,636	204,504
Mortgage
Segment Reporting Information
Total revenue	6,610	4,542	2,536
Marketing Funds
Segment Reporting Information
Total revenue	64,402	72,299
Other
Segment Reporting Information
Total revenue	4,197	5,816	5,586
Continuing franchise fees
Segment Reporting Information
Total revenue	90,217	99,928	101,104
Continuing franchise fees | Real Estate
Segment Reporting Information
Total revenue	84,863	95,854	98,828
Continuing franchise fees | Mortgage
Segment Reporting Information
Total revenue	5,354	4,074	2,276
Annual dues
Segment Reporting Information
Total revenue	35,075	35,409	35,894
Annual dues | Real Estate
Segment Reporting Information
Total revenue	35,075	35,409	35,894
Broker fees
Segment Reporting Information
Total revenue	50,028	45,990	46,871
Broker fees | Real Estate
Segment Reporting Information
Total revenue	50,028	45,990	46,871
Franchise sales and other revenue
Segment Reporting Information
Total revenue	26,279	28,667	28,757
Franchise sales and other revenue | Real Estate
Segment Reporting Information
Total revenue	20,826	22,383	22,911
Franchise sales and other revenue | Mortgage
Segment Reporting Information
Total revenue	$ 1,256	$ 468	$ 260