Commitments and Contingencies - Additional Information (Details) - USD ($)		1 Months Ended	12 Months Ended
	Jan. 02, 2018	Mar. 10, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 24, 2016
Other Commitments [Line Items]
Rental Expense Relating to Operating Leases			$ 39,485,000	$ 33,405,000	$ 34,180,000
Other Assets			65,073,000	62,474,000
Unfunded Commitments for Capital Contributions			3,408,000
Goodwill, Gross			169,838,000	189,461,000	194,961,000
Adjustments to Tax Receivable Agreements			77,535,000	0	0
Contractual Obligations Related To Tax Receivable Agreements			103,196,000
Payment To Counterparties To Tax Receivable Agreement Within One Year Or Less			12,821,000
Payment To Counterparties To Tax Receivable Agreement One To Three Years			17,421,000
Payment To Counterparties To Tax Receivable Agreement Three To Five Years			18,437,000
Payment To Counterparties To Tax Receivable Agreement After Five Years			$ 54,517,000
Inter-Bank Balance Interest Rate [Member]
Other Commitments [Line Items]
Debt Instrument, Basis Spread on Variable Rate			0.10%
BBVA Bancomer [Member]
Other Commitments [Line Items]
Maximum Borrowing Capacity			$ 10,222,000
PNC Bank [Member]
Other Commitments [Line Items]
Maximum Borrowing Capacity						$ 30,000,000
Amount Outstanding During Period		$ 30,000,000
Subsequent Event [Member] | PNC Bank [Member]
Other Commitments [Line Items]
Amount Outstanding During Period	$ 30,000,000
Protego [Member]
Other Commitments [Line Items]
Percentage of the Return Proceeds Received Payable (as a percent)			90.00%
Protego [Member] | Private Equity Funds [Member] | Discovery Fund [Member]
Other Commitments [Line Items]
Goodwill, Gross			$ 13,433,000
Office Equipment [Member]
Other Commitments [Line Items]
Rental Expense Relating to Operating Leases			2,394,000	2,449,000	$ 1,990,000
Letter of Credit [Member]
Other Commitments [Line Items]
Other Assets			$ 5,398,000	$ 5,387,000