Long-Term Incentive Compensation (Details Textual)	1 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended			9 Months Ended				9 Months Ended
	Feb. 28, 2014 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)	Mar. 31, 2014 Canadian Plan Westwood International Advisors Inc USD ($)	Jun. 30, 2013 Canadian Plan Westwood International Advisors Inc USD ($)	Sep. 30, 2014 Canadian Plan Westwood International Advisors Inc USD ($)	Sep. 30, 2014 Canadian Plan Maximum Westwood International Advisors Inc USD ($)	Sep. 30, 2014 Canadian Plan Maximum Westwood International Advisors Inc CAD	Sep. 30, 2014 Mutual Funds USD ($)	Sep. 30, 2013 Mutual Funds USD ($)	Dec. 31, 2013 Mutual Funds USD ($)	Sep. 30, 2014 Subsequent to 2014	Sep. 30, 2014 Restricted Stock USD ($)	Sep. 30, 2013 Restricted Stock USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total number of shares that may be issued under the Plan (including predecessor plans to the Plan)													3,898,100
Shares remain available for issuance													505,000
Remaining unrecognized compensation expense													$ 18,800,000
Remaining unrecognized compensation cost recognized over a remaining weighted average period													2 years
Adjusted pre-tax income	34,000,000
Annual growth rate period	5 years
Compound annual growth	10.00%
Nonvested restricted shares												185,252
Number of shares purchased in the open market				11,476	20,251
Amount of shares purchased in the open market		669,000	878,000	670,000	880,000
Purchase of treasury stock, shares						31,727
Fund purchases of common stock							8,900,000	10,000,000
Fund purchases of common stock remaining amount available to be paid						7,500,000
Mutual fund vesting period									1 year
Service period of mutual fund share incentive award									2 years
Expense related to mutual fund share incentive awards									700,000	1,800,000			10,103,000	8,512,000
Accrued liability related to mutual fund incentive awards									$ 600,000		$ 1,900,000