Summary of Significant Accounting Policies - Disaggregated 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
Disaggregation of Revenue [Line Items]
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
Disaggregation of Revenue [Line Items]
Total revenue									190,792	199,636	204,504
Company -Owned Regions
Disaggregation of Revenue [Line Items]
Total revenue									144,616	152,218	157,873
Independent Regions
Disaggregation of Revenue [Line Items]
Total revenue									34,423	34,467	33,082
Global and Other
Disaggregation of Revenue [Line Items]
Total revenue									11,753	12,951	13,549
Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue									64,402	72,299
Mortgage
Disaggregation of Revenue [Line Items]
Total revenue									6,610	4,542	2,536
Other
Disaggregation of Revenue [Line Items]
Total revenue									4,197	5,816	5,586
U.S. | Total Real Estate
Disaggregation of Revenue [Line Items]
Total revenue									157,448	164,867	170,496
U.S. | Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue									57,974	64,906
U.S. | Mortgage
Disaggregation of Revenue [Line Items]
Total revenue									6,610	4,542	2,536
U.S. | Other
Disaggregation of Revenue [Line Items]
Total revenue									4,197	5,816	5,586
Canada | Total Real Estate
Disaggregation of Revenue [Line Items]
Total revenue									21,769	23,024	23,771
Canada | Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue									5,634	6,559
Global | Total Real Estate
Disaggregation of Revenue [Line Items]
Total revenue									11,575	11,745	$ 10,237
Global | Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue									$ 794	$ 834