Segment information - Reportable Segments Revenue (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment									2
Continuing franchise fees									$ 73,750,000	$ 72,706,000	$ 64,465,000
Annual dues									31,758,000	30,726,000	29,524,000
Broker fees									32,334,000	28,685,000	24,811,000
Franchise sales and other franchise revenue									25,468,000	23,440,000	23,574,000
Brokerage Revenue									13,558,000	15,427,000	16,488,000
Total revenue	$ 43,274,000	$ 45,110,000	$ 44,277,000	$ 44,207,000	$ 42,565,000	$ 44,240,000	$ 42,299,000	$ 41,880,000	176,868,000	170,984,000	158,862,000
Amounts paid from brokerage services business	$ 43,274,000	$ 45,110,000	$ 44,277,000	$ 44,207,000	$ 42,565,000	$ 44,240,000	$ 42,299,000	$ 41,880,000	176,868,000	170,984,000	158,862,000
Real Estate Franchise Services
Segment Reporting Information [Line Items]
Continuing franchise fees									74,921,000	74,199,000	65,728,000
Annual dues									31,759,000	30,729,000	29,527,000
Broker fees									32,656,000	29,014,000	25,078,000
Franchise sales and other franchise revenue									25,561,000	23,459,000	23,577,000
Total revenue									164,897,000	157,401,000	143,910,000
Amounts paid from brokerage services business									164,897,000	157,401,000	143,910,000
Brokerages
Segment Reporting Information [Line Items]
Continuing franchise fees									(1,171,000)	(1,493,000)	(1,263,000)
Annual dues									(1,000)	(3,000)	(3,000)
Broker fees									(322,000)	(329,000)	(267,000)
Franchise sales and other franchise revenue									(93,000)	(19,000)	(3,000)
Brokerage Revenue									13,558,000	15,427,000	16,488,000
Total revenue									11,971,000	13,583,000	14,952,000
Amounts paid from brokerage services business									11,971,000	13,583,000	14,952,000
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total revenue									1,587,000	1,844,000	1,536,000
Amounts paid from brokerage services business									$ 1,587,000	$ 1,844,000	$ 1,536,000