Investments - Summary of Condensed Financial Information for Company's Equity Method Investments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statements of operations:
Total revenues	$ 65,430	$ 49,460	$ 49,033
Total expenses	67,711	68,973	64,987
Net loss	(2,281)	(19,513)	$ (15,954)
Statements of financial condition:
Total assets	68,020	28,826
Total equity and partners' capital	25,991	16,942
Total liabilities, equity and partners' capital	68,020	28,826
Cash and Cash Equivalents [Member]
Statements of financial condition:
Total assets	51,971	15,187
Fixed Assets, Net [Member]
Statements of financial condition:
Total assets	4,570	3,927
Other Assets [Member]
Statements of financial condition:
Total assets	11,479	9,712
Payables to Related Parties [Member]
Statements of financial condition:
Total liabilities	9,493	3,747
Other Liabilities [Member]
Statements of financial condition:
Total liabilities	$ 32,536	$ 8,137