Income taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
U.S. federal:
Current	$ 6	$ (402)	$ 1,651
Deferred	328	1,158	1,189
Total U.S. federal	334	756	2,840
U.S. state and local:
Current	226	248	327
Deferred	140	457	(202)
Total U.S. state and local	366	705	125
Reconciliation from U.S. federal statutory tax rate to effective income taxes rate
Federal statutory rate (as a percent)	34.00%	34.00%	34.00%
State and local (as a percent)	4.60%	(5.70%)	1.10%
Foreign rate differential (as a percent)	(0.70%)	(3.20%)
Stock options (as a percent)	(0.50%)	(0.70%)	(2.60%)
Non-controlling interests (as a percent)	1.90%	15.20%	(2.20%)
Valuation allowance (as a percent)	(45.10%)	(128.50%)
Transaction costs (as a percent)		(6.70%)
Purchase price adjustments (as a percent)		6.60%
Revaluation of deferred tax assets (as a percent)		2.80%
Uncertain tax positions (as a percent)	(0.10%)	(2.90%)
Return to provision (as a percent)	0.60%	9.30%	(5.30%)
Other (as a percent)	1.40%	1.10%	2.00%
Income taxes (as a percent)	(3.90%)	(78.70%)	27.00%
Deferred tax assets:
Net operating loss carryforwards	10,115	3,508
Outside basis differences for U.S. partnerships	3,710	2,842
Stock options	3,348	3,018
Deferred revenue	648	516
Deferred compensation	144	355
State taxes	45	34
Other	1,341	404
Valuation allowance	(12,470)	(4,101)	(1,669)
Net Deferred Tax Assets	6,881	6,576
Deferred tax liabilities:
Intangible assets	(6,855)	(6,737)
Property and equipment	(2,671)	(2,016)
Net deferred tax liabilities	(9,526)	(8,753)
Net deferred taxes	(2,645)	(2,177)
Net operating loss carryforwards
The tax effected amount of gross unnrealized net operating loss carryforwards excluded under ASC 718	6,284
Foreign loss before income taxes	1,251	559	61
Period of cumulative results for determination of releasing valuation allowance	3 years
Changes in the valuation allowance
Balance at the beginning of the period	4,101	1,669	1,822
Increase in valuation allowances on deferred tax assets	8,369	2,432	51
Decrease credited to operations			(204)
Balance at the end of the period	12,470	4,101	1,669
Windfall Tax Benefits from Stock Option Exercises		55	2,190
United Kingdom
Net operating loss carryforwards
Foreign subsidiary deferred tax asset	1,360
Brazil
Net operating loss carryforwards
Foreign subsidiary deferred tax asset	292
Federal
Net operating loss carryforwards
The tax effected amount of gross unnrealized net operating loss carryforwards excluded under ASC 718	35,555	20,389
State
Net operating loss carryforwards
The tax effected amount of gross unnrealized net operating loss carryforwards excluded under ASC 718	55,457	37,153
Foreign
Net operating loss carryforwards
The tax effected amount of gross unnrealized net operating loss carryforwards excluded under ASC 718	$ 7,661	$ 3,425