Consolidation - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash equivalents	$ 48,620	$ 54,772
Total assets measured at fair value	129,335	101,578
Level 1 [Member]
Assets
Cash equivalents	48,620	54,772
Total assets measured at fair value	129,335	101,578
Level 2 [Member]
Assets
Cash equivalents	0	0
Total assets measured at fair value	0	0
Level 3 [Member]
Assets
Cash equivalents	0	0
Total assets measured at fair value	0	0
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Derivatives	4	771
Total assets measured at fair value	142,079	324,106
Liabilities
Derivatives	300	972
Short sales	649	5,409
Total liabilities measured at fair value	949	6,381
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Debt Securities [Member]
Assets
Investments and bank loans	101,597	152,553
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Equity securities [Member]
Assets
Investments and bank loans	40,478	170,782
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Assets
Derivatives	4	33
Total assets measured at fair value	40,274	163,019
Liabilities
Derivatives	3	128
Short sales	649	5,334
Total liabilities measured at fair value	652	5,462
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| Debt Securities [Member]
Assets
Investments and bank loans	0	0
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| Equity securities [Member]
Assets
Investments and bank loans	40,270	162,986
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Assets
Derivatives	0	738
Total assets measured at fair value	101,718	159,690
Liabilities
Derivatives	235	844
Short sales	0	75
Total liabilities measured at fair value	235	919
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Debt Securities [Member]
Assets
Investments and bank loans	101,510	151,156
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Equity securities [Member]
Assets
Investments and bank loans	208	7,796
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Assets
Derivatives	0	0
Total assets measured at fair value	87	1,397
Liabilities
Derivatives	62	0
Short sales	0	0
Total liabilities measured at fair value	62	0
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 3 [Member] \| Debt Securities [Member]
Assets
Investments and bank loans	87	1,397
Consolidated Sponsored Investment Products [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 3 [Member] \| Equity securities [Member]
Assets
Investments and bank loans	0	0
Consolidated Investment Product [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Cash equivalents	14,449	8,297
Investments and bank loans	346,967	199,485
Total assets measured at fair value	361,416	207,782
Liabilities
Notes payable	328,761
Total liabilities measured at fair value	328,761
Consolidated Investment Product [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Assets
Cash equivalents	14,449	8,297
Investments and bank loans	0	0
Total assets measured at fair value	14,449	8,297
Liabilities
Notes payable	0
Total liabilities measured at fair value	0
Consolidated Investment Product [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Assets
Cash equivalents	0	0
Investments and bank loans	346,967	199,485
Total assets measured at fair value	346,967	199,485
Liabilities
Notes payable	328,761
Total liabilities measured at fair value	328,761
Consolidated Investment Product [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Assets
Cash equivalents	0	0
Investments and bank loans	0	0
Total assets measured at fair value	0	$ 0
Liabilities
Notes payable	0
Total liabilities measured at fair value	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value of obligations incurred from short sales.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Fair value portion of notes payable.

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