Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014
Investments
Assets
Assets beginning balance	[1]	$ 9,508	[2]	$ 5,946
Total Realized and Unrealized Gains (Losses)		(944)	[2],[3],[4]	101	[1],[5],[6]
Purchases and Issuances		437	[2]	5,178	[1]
Sales and Settlements		(738)	[2]	(1,717)	[1]
Assets ending balance	[2]	8,263		9,508	[1]
Interest rate lock commitments
Assets
Assets beginning balance	[8]	7,576	[7]	2,375
Total Realized and Unrealized Gains (Losses)		1,585	[3],[4],[7]	5,201	[5],[6],[8]
Assets ending balance	[7]	9,161		7,576	[8]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities beginning balance	[8]	1,222	[7]	3,653
Total Realized and Unrealized Gains (Losses)		299	[3],[4],[7]	2,431	[5],[6],[8]
Liabilities ending balance	[7]	923		1,222	[8]
Auction rate securities
Assets
Assets beginning balance	[9],[11],[13]	91,422	[10],[12],[14]	85,124
Total Realized and Unrealized Gains (Losses)		1,955	[3],[4],[10],[12],[14]	(622)	[5],[6],[9],[11],[13]
Purchases and Issuances		17,950	[10],[12],[14]	20,625	[9],[11],[13]
Sales and Settlements		(24,525)	[10],[12],[14]	(13,705)	[9],[11],[13]
Assets ending balance	[10],[12],[14]	86,802		91,422	[9],[11],[13]
ARS purchase commitments
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities beginning balance	[15]	902	[16]	2,600
Total Realized and Unrealized Gains (Losses)		(467)	[3],[4],[16]	1,698	[5],[6],[15]
Liabilities ending balance	[16]	1,369		902	[15]
Municipal obligations
Assets
Assets beginning balance		164		236
Total Realized and Unrealized Gains (Losses)		(63)	[3],[4]	(72)	[5],[6]
Sales and Settlements		(20)
Assets ending balance		$ 81		$ 164

[1] Primarily represents general partner ownership and limited partner interests in hedge funds and private equity funds sponsored by the Company.

[2] Primarily represents general partner ownership and limited partner interests in hedge funds and private equity funds sponsored by the Company.

[3] Included in principal transactions on the consolidated statement of income, except for investments which are included in other income on the consolidated statement of income.

[4] Unrealized gains (losses) are attributable to assets or liabilities that are still held at the reporting date.

[5] Included in principal transactions on the consolidated statement of income, except for investments which are included in other income on the consolidated statement of income.

[6] Unrealized gains (losses) are attributable to assets or liabilities that are still held at the reporting date.

[7] Interest rate lock commitment assets and liabilities are recorded upon the commitment to originate a loan with a borrower and sell the loan to an investor. The commitment assets and liabilities are recognized at fair value, which reflects the fair value of the contractual loan origination related fees and sale premiums, net of co-broker fees, and the estimated fair value of the expected net future cash flows associated with the servicing of the loan

[8] Interest rate lock commitment assets and liabilities are recorded upon the commitment to originate a loan with a borrower and sell the loan to an investor. The commitment assets and liabilities are recognized at fair value, which reflects the fair value of the contractual loan origination related fees and sale premiums, net of co-broker fees, and the estimated fair value of the expected net future cash flows associated with the servicing of the loan.

[9] Purchases and issuances in connection with ARS purchase commitments represent instances in which the Company purchased ARS securities from clients during the period pursuant to regulatory and legal settlements and awards that satisfy the outstanding commitment to purchase obligation. This also includes instances where the ARS issuer has redeemed ARS where the Company had an outstanding purchase commitment prior to the Company purchasing those ARS.

[10] Purchases and issuances in connection with ARS purchase commitments represent instances in which the Company purchased ARS securities from clients during the period pursuant to regulatory and legal settlements and awards that satisfy the outstanding commitment to purchase obligation. This also includes instances where the ARS issuer has redeemed ARS where the Company had an outstanding purchase commitment prior to the Company purchasing those ARS.

[11] Represents auction rate preferred securities, municipal auction rate securities and student loan auction rate securities that failed in the auction rate market.

[12] Represents auction rate preferred securities, municipal auction rate securities and student loan auction rate securities that failed in the auction rate market.

[13] Sales and settlements for the ARS purchase commitments represent additional purchase commitments made during the year for regulatory and legal ARS settlements and awards.

[14] Sales and settlements for the ARS purchase commitments represent additional purchase commitments made during the year for regulatory and legal ARS settlements and awards.

[15] Represents the difference in principal and fair value for auction rate securities purchase commitments outstanding at the end of the year.

[16] Represents the difference in principal and fair value for auction rate securities purchase commitments outstanding at the end of the year.