Commitments and Contingencies - Additional Information (Detail) - USD ($)			12 Months Ended
	Jan. 27, 2016	Feb. 05, 2015	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 15, 2016	Jun. 26, 2015	Mar. 31, 2015
Commitment And Contingencies [Line Items]
Operating lease agreements expiration date				Various dates through 2025
Rental expense relating to operating leases				$ 34,180,000	$ 27,375,000	$ 23,905,000
Other Assets				39,290,000	30,609,000
Unfunded commitments for capital contributions				8,162,000
Line Of Credit Intra Day Facility				11,560,000
Contractual Obligations Related To Tax Receivable Agreements				197,674,000
Payment To Counterparties To Tax Receivable Agreement Within One Year Or Less				11,638,000
Payment To Counterparties To Tax Receivable Agreement One To Three Years				23,713,000
Payment To Counterparties To Tax Receivable Agreement Three To Five Years				25,590,000
Payment To Counterparties To Tax Receivable Agreement After Five Years				136,733,000
Goodwill				194,961,000
Investment in private equity funds				86,287,000	76,581,000
Other Commitment									$ 5,500,000
Loans and Leases Receivable, Gross				3,500,000
Remaining Loan Commitment				2,000,000
Loss Contingency, Damages Sought, Value				$ 300,000,000
Basis Spread on Overnight Facility				0.10%
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				$ 26,473,000	36,551,000
Private Equity Funds [Member] | Discovery Fund [Member]
Commitment And Contingencies [Line Items]
Investment in private equity funds				6,632,000	2,867,000
Private Equity Funds [Member] | Discovery Fund [Member] | Protego [Member]
Commitment And Contingencies [Line Items]
Goodwill				4,713,000
Investment in private equity funds				$ 6,632,000
Scenario, Forecast [Member]
Commitment And Contingencies [Line Items]
Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions			20.00%
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
Letter of Credit [Member]
Commitment And Contingencies [Line Items]
Other Assets				$ 5,086,000	3,308,000
Office Equipment [Member]
Commitment And Contingencies [Line Items]
Rental expense relating to operating leases				$ 1,990,000	$ 1,640,000	$ 1,049,000
Subsequent Event [Member] | First Republic Bank [Member]
Commitment And Contingencies [Line Items]
Maximum borrowing capacity							$ 50,000,000
Amount outstanding during period	$ 50,000,000
Inter-Bank Balance Interest Rate [Member]
Commitment And Contingencies [Line Items]
Debt Instrument, Basis Spread on Variable Rate				0.10%