Variable Interest Entities (Details Textual) In Millions, unless otherwise specified	3 Months Ended		1 Months Ended
	Mar. 31, 2015 USD ($) Number_of_Limited_Partnership Number_of_Limited_Liability_Companies	Mar. 31, 2014 USD ($)	Oct. 31, 2014 UCITS Fund USD ($)	Oct. 31, 2014 UCITS Fund EUR (€)	Jan. 31, 2015 Common Trust Funds USD ($)	Jan. 31, 2014 Common Trust Funds USD ($)
Variable Interest Entity [Line Items]
Number of limited liability companies in which some clients hold their investments	10
Number of clients in which investment advisory services are provided	2
Amount provided to fund for the sole purpose of showing economic substance			$ 2.0	€ 1.6	$ 1.0	$ 2.0
Fee revenues from Westwood VIEs	$ 14.3	$ 11.2