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The amount of identifiable intangible assets recognized as of the acquisition date.

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Investments - Additional Information (Detail)	12 Months Ended				12 Months Ended	0 Months Ended	12 Months Ended
Investments - Additional Information (Detail)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2014 Maximum [Member] USD ($)	Apr. 09, 2013 Kleinwort Benson Investors International, Ltd. [Member]	Dec. 31, 2014 Kleinwort Benson Investors International, Ltd. [Member]	Apr. 09, 2013 Kleinwort Benson Investors International, Ltd. [Member] USD ($)	Apr. 09, 2013 Kleinwort Benson Investors International, Ltd. [Member] EUR (€)
Investment [Line Items]
Realized gain on trading securities	$ 8,200,000	$ 1,000,000	$ 400,000
Interest acquired in limited partnership	5,000,000
Future capital commitment					6,700,000
Acquisition date							Apr. 09, 2013
Percentage of noncontrolling equity interest acquired	50.00%							24.00%	24.00%
Noncontrolling equity interest acquired, amount								3,400,000	2,600,000
Investment to goodwill	5,260,000us-gaap_Goodwill	5,260,000us-gaap_Goodwill	5,260,000us-gaap_Goodwill	4,795,000us-gaap_Goodwill				2,500,000
Definite-lived intangible assets								600,000
Period of amortization of definite-lived intangible assets						7 years
Remaining assets and liabilities								$ 300,000