Summary of Significant Accounting Policies - Disaggregated revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 77,246	$ 52,207	$ 149,541	$ 122,479
Franchise sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	5,927	4,533	14,078	14,775
Total Real Estate
Disaggregation of Revenue [Line Items]
Total revenue	56,291	38,371	107,445	88,276
Total Real Estate | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	51,361	34,966	95,595	76,208
Total Real Estate | Franchise sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	4,930	3,405	11,850	12,068
Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	18,042	11,765	36,187	29,287
Mortgage
Disaggregation of Revenue [Line Items]
Total revenue	2,410	1,070	4,733	2,528
Mortgage | Franchise sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	494	127	1,052	319
Other
Disaggregation of Revenue [Line Items]
Total revenue	503	1,001	1,176	2,388
U.S. | Company -Owned Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	37,613	25,511	70,159	56,089
U.S. | Independent Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	3,730	3,167	7,018	6,163
U.S. | Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	16,359	10,596	32,541	26,247
U.S. | Mortgage
Disaggregation of Revenue [Line Items]
Total revenue	2,410	1,070	4,733	2,528
U.S. | Other
Disaggregation of Revenue [Line Items]
Total revenue	503	1,001	1,176	2,388
Canada | Company -Owned Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	4,800	2,459	8,354	5,540
Canada | Independent Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	2,364	2,033	4,569	4,072
Canada | Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	1,424	1,015	3,161	2,670
Global | Global. | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	2,854	1,796	5,495	4,344
Global | Total Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	$ 259	$ 154	$ 485	$ 370