Consolidated Sponsored Investment Products - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2014 Funds	Jun. 30, 2014 Funds	Dec. 31, 2013 Funds	Jun. 30, 2013
Investments [Abstract]
Number of consolidated sponsored investment products	11	11	8
Number of additional consolidated sponsored investment product		4
Number of deconsolidated sponsored investment product		1
Changes in market value of investments	$ 0	$ 0
Fair value, equity, Level 1 to Level 2 transfers, amount	$ 0	$ 0		$ 0

Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)

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

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration