Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
	Dec. 31, 2017 USD ($) reporting_units	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Schedule Of Significant Accounting Policies [Line Items]
Provision for income taxes	$ 13,904,000	$ 11,363,000	$ 15,115,000
Foreign Currency Transaction Gain (Loss), before Tax	$ 1,600,000	(362,000)	(544,000)
Number of reporting units | reporting_units	2
Goodwill impairment loss	$ 0	0	0
Valuation allowance	0
Uncertain tax position	160,000	2,462,000	$ 1,629,000
Unrecognized tax benefits	$ 46,000	$ 942,000
Effective Income Tax Rate Reconciliation, Percent	41.00%	33.40%	35.80%
Furniture and fixtures | Minimum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	3 years
Furniture and fixtures | Maximum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	7 years
Leasehold improvements
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	lesser of the estimated useful life or lease term
Westwood International Advisors Inc | Canadian Plan
Schedule Of Significant Accounting Policies [Line Items]
Compensation expense recorded	$ 232,000	$ 524,000	$ 145,000
Retained Earnings
Schedule Of Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(711,000)
Adoption of ASU 2016-09 [Member]
Schedule Of Significant Accounting Policies [Line Items]
Provision for income taxes	$ 1,000,000
Effective Income Tax Rate Reconciliation, Percent	2.90%
Tax rate excluding ASU 2016-09 adoption	43.90%