Commitments and Contingencies - Additional Information (Detail) - USD ($)		3 Months Ended		6 Months Ended		12 Months Ended
	Feb. 05, 2015	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2017	Jun. 26, 2015	Mar. 31, 2015	Dec. 31, 2014
Commitment And Contingencies [Line Items]
Operating lease agreements expiration date				Various dates through 2023
Rental expense relating to operating leases		$ 8,488,000	$ 6,895,000	$ 17,359,000	$ 13,279,000
Unfunded commitments for capital contributions		8,504,000		8,504,000
Investment in private equity funds		71,581,000		71,581,000					$ 76,581,000
Other Commitment								$ 5,500,000
Loans and Leases Receivable, Gross		3,500,000		3,500,000
Remaining Loan Commitment		2,000,000		2,000,000
Loss Contingency, Damages Sought, Value				$ 300,000,000
First Republic Bank [Member]
Commitment And Contingencies [Line Items]
Maximum borrowing capacity							$ 75,000,000
Line of Credit Facility, Expiration Date				Jun. 27, 2016
Amount outstanding during period	$ 45,000,000
Protego [Member]
Commitment And Contingencies [Line Items]
Percentage of the return proceeds received payable (as a percent)				90.00%
Private Equity Funds [Member]
Commitment And Contingencies [Line Items]
Investment in private equity funds		26,985,000		$ 26,985,000					36,551,000
Private Equity Funds [Member] | Discovery Fund [Member]
Commitment And Contingencies [Line Items]
Investment in private equity funds		3,711,000		3,711,000					$ 2,867,000
Private Equity Funds [Member] | Discovery Fund [Member] | Protego [Member]
Commitment And Contingencies [Line Items]
Goodwill		1,862,000		1,862,000
Investment in private equity funds		$ 3,711,000		$ 3,711,000
Scenario, Forecast [Member]
Commitment And Contingencies [Line Items]
Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions						20.00%