Segment Information - Additional Information (Detail) (USD $)	3 Months Ended
Mar. 31, 2013 Business
Segment Reporting [Abstract]
Number of businesses	4
Assets under management	$ 624,000,000
Assets under administration	$ 16,400,000,000

The carrying amount of assets an investment adviser manages on behalf of investors.

No definition available.

Name:	us-gaap_AssetsUnderManagementCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant