Summary of Significant Accounting Policies - Disaggregated revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 72,295	$ 70,272
Franchise sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	8,151	10,242
Total Real Estate
Disaggregation of Revenue [Line Items]
Total revenue	51,154	49,905
Total Real Estate | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	44,234	41,242
Total Real Estate | Franchise sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	6,920	8,663
Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	18,145	17,522
Mortgage
Disaggregation of Revenue [Line Items]
Total revenue	2,323	1,458
Mortgage | Franchise sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	558	192
Other
Disaggregation of Revenue [Line Items]
Total revenue	673	1,387
U.S. | Company -Owned Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	32,546	30,578
U.S. | Independent Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	3,288	2,996
U.S. | Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	16,182	15,651
U.S. | Mortgage
Disaggregation of Revenue [Line Items]
Total revenue	2,323	1,458
U.S. | Other
Disaggregation of Revenue [Line Items]
Total revenue	673	1,387
Canada | Company -Owned Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	3,554	3,081
Canada | Independent Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	2,205	2,039
Canada | Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	1,737	1,655
Global | Global. | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	2,641	2,548
Global | Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	$ 226	$ 216