Commitments and Contingencies - Additional Information (Detail) (USD $) Share data in Thousands, unless otherwise specified	3 Months Ended			9 Months Ended				3 Months Ended	9 Months Ended		9 Months Ended						1 Months Ended			0 Months Ended
	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Aug. 03, 2014	Dec. 31, 2013	Sep. 30, 2014 First Republic Bank [Member]	Sep. 30, 2014 First Republic Bank [Member]	Dec. 31, 2013 First Republic Bank [Member]	Sep. 30, 2014 Protego [Member]	Sep. 30, 2014 Private Equity Funds [Member]	Dec. 31, 2013 Private Equity Funds [Member]	Sep. 30, 2014 Private Equity Funds [Member] Discovery Fund [Member]	Dec. 31, 2013 Private Equity Funds [Member] Discovery Fund [Member]	Sep. 30, 2014 Private Equity Funds [Member] Discovery Fund [Member] Protego [Member]	Apr. 30, 2014 EWM [Member]	May 22, 2014 EWM [Member]	Aug. 03, 2014 Institutional Equities [Member]	Aug. 03, 2014 Class E LP Units [Member]	Aug. 03, 2014 Class G And H Interests [Member]
Commitment And Contingencies [Line Items]
Operating lease agreements expiration date				Various dates through 2023
Rental expense relating to operating leases	$ 6,619,000		$ 5,926,000	$ 19,898,000	$ 17,787,000
Operating Leases, Rent Expense, Minimum Rentals		2,000,000
Unfunded commitments for capital contributions	9,177,000			9,177,000
Percentage of the return proceeds received payable (as a percent)											90.00%
Goodwill																2,162,000
Investment in private equity funds	76,593,000			76,593,000			67,560,000					35,635,000	32,379,000	2,673,000	5,015,000	2,673,000
Maximum borrowing capacity										25,000,000
Line of Credit Facility, Initiation Date									Jun. 24, 2014
Line of Credit Facility, Expiration Date									Jun. 27, 2015
Amount outstanding during period								25,000,000
Commitment to purchase noncontrolling interest (in shares)																	3
Commitment to purchase noncontrolling interest (as a percent)																	22.00%		40.00%
Purchase of interest by parent																	7,100,000
Ownership Parent (as a percent)																		62.00%
Grant Of LP Units (in units)	72																11			2,583	5,437
Business Acquisitions Contingent Consideration Potential Cash Payment	$ 3,391,000			$ 3,391,000		$ 11,086,000