Consolidated Sponsored Investment Products - Condensed Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Total cash	$ 194,334	$ 202,847
Total investments	59,301	63,448
All other assets	14,326	16,060
Total assets	721,998	698,773
Total liabilities	107,468	112,350
Redeemable noncontrolling interest	55,557	23,071
Equity attributable to stockholders of the Company	559,363	563,542
Non-redeemable noncontrolling interest	(390)	(190)
Total liabilities and equity	721,998	698,773
Balances as Reported in Consolidated Balance Sheet [Member]
Condensed Financial Statements, Captions [Line Items]
Total cash	206,594	211,534
Total investments	330,298	300,100
All other assets	185,106	187,139
Total assets	721,998	698,773
Total liabilities	107,468	112,350
Redeemable noncontrolling interest	55,557	23,071
Equity attributable to stockholders of the Company	559,363	563,542
Non-redeemable noncontrolling interest	(390)	(190)
Total liabilities and equity	721,998	698,773
Reportable Legal Entities [Member] \| Balance Before Consolidation of Investment Products [Member]
Condensed Financial Statements, Captions [Line Items]
Total cash	194,334	202,847
Total investments	276,253	279,863
All other assets	176,399	180,436
Total assets	646,986	663,146
Total liabilities	88,013	99,794
Equity attributable to stockholders of the Company	559,363	563,542
Non-redeemable noncontrolling interest	(390)	(190)
Total liabilities and equity	646,986	663,146
Reportable Legal Entities [Member] \| Consolidated Sponsored Investment Products [Member]
Condensed Financial Statements, Captions [Line Items]
Total cash	12,260	8,687
Total investments	270,997	236,652
All other assets	8,960	6,960
Total assets	292,217	252,299
Total liabilities	19,708	12,813
Equity attributable to stockholders of the Company	272,509	239,486
Total liabilities and equity	292,217	252,299
Eliminations and Adjustments [Member]
Condensed Financial Statements, Captions [Line Items]
Total investments	(216,952)	(216,415)
All other assets	(253)	(257)
Total assets	(217,205)	(216,672)
Total liabilities	(253)	(257)
Redeemable noncontrolling interest	55,557	23,071
Equity attributable to stockholders of the Company	(272,509)	(239,486)
Total liabilities and equity	$ (217,205)	$ (216,672)

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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