Segment Information - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information
Total revenue	$ 72,449	$ 71,073	$ 52,207	$ 70,272	$ 68,193	$ 71,541	$ 71,381	$ 71,178	$ 266,001	$ 282,293	$ 212,626
Total 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 fees
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 | Total 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 | Total 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 | Total 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 | Total 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