Consolidation of Sponsored Investment Products - Consolidated Statement of Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Current assets	$ 200,825	$ 164,826
Non-current assets	141,775	167,923
Total assets	342,600	332,749
Current liabilities	54,156	62,411
Non-current liabilities	22,642	22,704
Total liabilities	76,798	85,115
Redeemable noncontrolling interest	9,421	3,163
Equity attributable to stockholders of the Company	256,416	244,474
Non-redeemable noncontrolling interest	(35)	(3)
Total liabilities and equity	342,600	332,749
Balance Before Consolidation of Investment Products [Member]
Condensed Financial Statements, Captions [Line Items]
Current assets	190,535	161,286
Non-current assets	141,775	167,923
Total assets	332,310	329,209
Current liabilities	53,287	62,034
Non-current liabilities	22,642	22,704
Total liabilities	75,929	84,738
Redeemable noncontrolling interest
Equity attributable to stockholders of the Company	256,416	244,474
Non-redeemable noncontrolling interest	(35)	(3)
Total liabilities and equity	332,310	329,209
Consolidated Investment Products [Member]
Condensed Financial Statements, Captions [Line Items]
Current assets	44,813	43,924
Non-current assets
Total assets	44,813	43,924
Current liabilities	867	364
Non-current liabilities
Total liabilities	867	364
Redeemable noncontrolling interest
Equity attributable to stockholders of the Company	43,946	43,560
Non-redeemable noncontrolling interest
Total liabilities and equity	44,813	43,924
Eliminations and Adjustments [Member]
Condensed Financial Statements, Captions [Line Items]
Current assets	(34,523)	(40,384)
Non-current assets
Total assets	(34,523)	(40,384)
Current liabilities	2	13
Non-current liabilities
Total liabilities	2	13
Redeemable noncontrolling interest	9,421	3,163
Equity attributable to stockholders of the Company	(43,946)	(43,560)
Non-redeemable noncontrolling interest
Total liabilities and equity	$ (34,523)	$ (40,384)

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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