Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Westwood Funds
Variable Interest Entities
Assets Under Management	$ 2,372	$ 1,603
Corporate Investment	13.1	10.9
Risk of Loss	13.1	10.9
Common Trust Funds
Variable Interest Entities
Assets Under Management	2,516	2,091
Corporate Investment		4.5
Risk of Loss		4.5
Collective Investment Trusts
Variable Interest Entities
Assets Under Management	449	366
Corporate Investment
Risk of Loss
LLCs
Variable Interest Entities
Assets Under Management	148	255
Corporate Investment
Risk of Loss
UCITS Fund
Variable Interest Entities
Assets Under Management	381
Corporate Investment
Risk of Loss