Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Categorization of Investments and Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table presents the categorization of investments and certain other financial assets measured at fair value on a recurring basis as of December 31, 2017 and 2016:

	December 31, 2017
	Level I		Level II		Level III		Total
Corporate Bonds, Municipal Bonds and Other Debt Securities(1)	$	—	$	44,648	$	—	$	44,648
Securities Investments(1)	4,336		1,795		—		6,131
Investment Funds	27,699		—		—		27,699
Financial Instruments Owned and Pledged as Collateral at Fair Value	19,374		—		—		19,374
Total Assets Measured At Fair Value	$	51,409	$	46,443	$	—	$	97,852
	December 31, 2016
	Level I		Level II		Level III		Total
Corporate Bonds, Municipal Bonds and Other Debt Securities(1)	$	—	$	44,630	$	—	$	44,630
Securities Investments(1)	3,794		1,728		—		5,522
Investment Funds	25,508		—		—		25,508
Financial Instruments Owned and Pledged as Collateral at Fair Value	18,535		—		—		18,535
Total Assets Measured At Fair Value	$	47,837	$	46,358	$	—	$	94,195

(1) Includes $13,446 and $9,173 of treasury bills, municipal bonds and commercial paper classified within Cash and Cash Equivalents on the Consolidated Statements of Financial Condition as of December 31, 2017 and 2016, respectively.

Carrying Amount and Estimated Fair Value of Financial Instrument Assets and Liabilities which are Not Measured at Fair Value

The carrying amount and estimated fair value of the Company's financial instrument assets and liabilities, which are not measured at fair value on the Consolidated Statements of Financial Condition, are listed in the tables below.

			December 31, 2017
	Carrying		Estimated Fair Value
	Amount		Level I		Level II		Level III		Total
Financial Assets:
Cash and Cash Equivalents	$	596,141	$	596,141	$	—	$	—	$	596,141
Certificates of Deposit	63,527		—		63,527		—		63,527
Debt Security Investment	10,995		—		—		10,995		10,995
Securities Purchased Under Agreements to Resell	10,645		—		10,645		—		10,645
Accounts Receivable	184,993		—		184,993		—		184,993
Receivable from Employees and Related Parties	17,030		—		17,030		—		17,030
Closely-held Equity Security	1,079		—		—		1,079		1,079
Financial Liabilities:
Accounts Payable and Accrued Expenses	$	34,111	$	—	$	34,111	$	—	$	34,111
Securities Sold Under Agreements to Repurchase	30,027		—		30,027		—		30,027
Payable to Employees and Related Parties	31,167		—		31,167		—		31,167
Notes Payable	168,347		—		171,929		—		171,929
Subordinated Borrowings	6,799		—		6,859		—		6,859
			December 31, 2016
	Carrying		Estimated Fair Value
	Amount		Level I		Level II		Level III		Total
Financial Assets:
Cash and Cash Equivalents	$	549,351	$	549,351	$	—	$	—	$	549,351
Securities Purchased Under Agreements to Resell	12,585		—		12,585		—		12,585
Accounts Receivable	230,522		—		230,522		—		230,522
Receivable from Employees and Related Parties	15,034		—		15,034		—		15,034
Assets Segregated for Bank Regulatory Requirements	10,200		10,200		—		—		10,200
Closely-held Equity Security	1,079		—		—		1,079		1,079
Financial Liabilities:
Accounts Payable and Accrued Expenses	$	30,723	$	—	$	30,723	$	—	$	30,723
Securities Sold Under Agreements to Repurchase	31,150		—		31,150		—		31,150
Payable to Employees and Related Parties	27,366		—		27,366		—		27,366
Notes Payable	168,097		—		170,251		—		170,251
Subordinated Borrowings	16,550		—		16,803		—		16,803