Consolidated Sponsored Investment Products - Additional Information (Detail) (USD $)	3 Months Ended
Mar. 31, 2014 Funds	Dec. 31, 2013 Funds	Mar. 31, 2013
Investments [Abstract]
Number of consolidated sponsored investment products	8	8
Number of additional consolidated sponsored investment product	1
Number of deconsolidated sponsored investment product	1
Fair value, equity, Level 1 to Level 2 transfers, amount	$ 0		$ 0

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bb)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

Name:	us-gaap_FairValueAssetsLevel1ToLevel2TransfersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant