Summary of Significant Accounting Policies - Disaggregated revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Total revenue	$ 91,004	$ 72,295
Franchise sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	10,649	8,151
Real Estate
Disaggregation of Revenue [Line Items]
Total revenue	64,737	51,154
Real Estate | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	55,125	44,234
Real Estate | Franchise sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	9,612	6,920
Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	22,851	18,145
Mortgage
Disaggregation of Revenue [Line Items]
Total revenue	3,028	2,323
Mortgage | Franchise sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	649	558
Other.
Disaggregation of Revenue [Line Items]
Total revenue	388	673
U.S. | Company -Owned Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	39,154	32,546
U.S. | Independent Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	1,701	3,288
U.S. | Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	17,559	16,182
Canada | Company -Owned Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	10,475	3,554
Canada | Independent Regions | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	703	2,205
Canada | Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	5,013	1,737
Global | Global. | Fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	3,092	2,641
Global | Marketing Funds
Disaggregation of Revenue [Line Items]
Total revenue	$ 279	$ 226