Related Party Transactions (Details)						1 Months Ended				3 Months Ended	12 Months Ended					120 Months Ended
	Oct. 26, 2016 USD ($) shares	Feb. 15, 2015 USD ($) shares	Feb. 03, 2015 USD ($)	Nov. 14, 2014 USD ($) shares	Nov. 04, 2011 USD ($)	Mar. 31, 2014 USD ($)	Jan. 31, 2013 USD ($) shares	Sep. 30, 2012 ft² extension	May 31, 2009 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2008 USD ($)	Dec. 31, 2015 USD ($) investment	Feb. 21, 2017	Dec. 01, 2016 $ / shares	Nov. 30, 2016 shares	Mar. 14, 2014	Dec. 31, 2013 USD ($) shares	May 31, 2013 USD ($)	Sep. 10, 2012 USD ($)	May 11, 2009 USD ($)
Related Party Transaction [Line Items]
Maturities of investment securities												$ 10,822,000	$ 5,491,000	$ 930,000
Gross realized gains on sales												3,408,000	13,727,000	275,000
Impairment of investment securities												$ 5,381,000	12,846,000	$ 0
Operating lease term												1 year
Convertible Debt | 6.75% Variable Interest Senior Convertible Exchange Notes due 2014
Related Party Transaction [Line Items]
Interest rate				6.75%										6.75%						6.75%				6.75%
Convertible Debt | 6.75% Variable Interest Senior Convertible Note due 2015
Related Party Transaction [Line Items]
Principal amount																								$ 50,000,000
Interest rate		6.75%
Convertible principal balance			$ 25,000,000
Ladenburg Thalmann Financial Services Inc.
Related Party Transaction [Line Items]
Investment owned (in shares) | shares												15,191,205
Equity method ownership percentage												8.28%
Castle Brands Inc.
Related Party Transaction [Line Items]
Investment owned (in shares) | shares												12,671,159
Morgans Hotel Group Co.
Related Party Transaction [Line Items]
Investment owned (in shares) | shares																			2,459,788
Investment owned percent																			7.03%
Equity Method Investee | Ladenburg Thalmann Financial Services Inc.
Related Party Transaction [Line Items]
Equity method ownership percentage												8.28%
Revenue from related parties												$ 850,000	850,000	$ 850,000
Equity Method Investee | Ladenburg Thalmann Financial Services Inc. | Forecast
Related Party Transaction [Line Items]
Revenue from related parties											$ 850,000
Equity Method Investee | Ladenburg Thalmann Financial Services Inc. | LTS Loan Due Nov 2016
Related Party Transaction [Line Items]
Debt instrument term					5 years
Loan receivable					$ 15,000,000
Interest rate on receivable					11.00%
Interest income												$ 205,000	280,000	574,000
Amount of debt surrendered or exchanged for equity in investee	$ 1,680,000
Equity Method Investee | Ladenburg Thalmann Financial Services Inc. | LTS Warrants
Related Party Transaction [Line Items]
Investment warrants outstanding (in shares) | shares	1,000,000
Equity Method Investee | Ladenburg Thalmann Financial Services Inc. | LTS Preferred | Series A Cumulative Redeemable Preferred Stock
Related Party Transaction [Line Items]
Investment owned (in shares) | shares												240,000
Interest income												$ 480,000	480,000
Preferred stock dividend rate												8.00%
Liquidation preference (in dollars per share) | $ / shares												$ 25
Equity Method Investee | Castle Brands Inc.
Related Party Transaction [Line Items]
Revenue from related parties												$ 100,000	100,000	100,000
Equity Method Investee | Castle Brands Inc. | Forecast
Related Party Transaction [Line Items]
Revenue from related parties											$ 100,000
Equity Method Investee | Castle Brands Inc. | Convertible Debt
Related Party Transaction [Line Items]
Principal amount																					$ 200,000
Interest rate																					5.00%
Convertible share (in shares) | shares																					222,222
President and Chief Executive Officer | Insurance Commissions
Related Party Transaction [Line Items]
Amount of transaction												247,000	217,000	261,000
President and Chief Executive Officer | Reserved Unit in Real Estate Venture
Related Party Transaction [Line Items]
Amount of transaction													5,200,000
President and Chief Executive Officer | Ladenburg Thalmann Financial Services Inc. | Compensation Paid to Vice Chairman of LTS
Related Party Transaction [Line Items]
Amount of transaction												1,250,000	1,300,000	1,375,000
President and Chief Executive Officer | Ladenburg Thalmann Financial Services Inc. | Director Fees Paid to Vice Chairman of LTS
Related Party Transaction [Line Items]
Amount of transaction												36,000	38,000	39,000
Executive Vice President | Ladenburg Thalmann Financial Services Inc. | Compensation Paid to President and CEO of LTS
Related Party Transaction [Line Items]
Amount of transaction												1,450,000	1,450,000	1,375,000
Beneficial Owner | Dr. Phillip Frost [Member]
Related Party Transaction [Line Items]
Ownership percentage by shareholders					15.30%
Percent of ownership by management (more than 10%)																10.00%
Beneficial Owner | Dr. Phillip Frost [Member] | Subsequent Event
Related Party Transaction [Line Items]
Ownership percentage by shareholders																	15.30%
Investee | Morgans Hotel Group Co.
Related Party Transaction [Line Items]
Warrants exercise price (in dollars per share) | $ / shares																		$ 2.25
Maturities of investment securities										$ 5,535,000
Gross realized gains on sales										2,140,000
Impairment of investment securities										$ 4,772,000
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Number of investments | investment																3
Affiliated Entity [Member] | Entity Affiliated with Dr. Frost | Convertible Debt | 6.75% Variable Interest Senior Convertible Exchange Notes due 2014
Related Party Transaction [Line Items]
Principal amount									$ 50,000,000
Interest rate									6.75%
Payments for purchase of private placement									$ 38,225,000
Convertible principal balance		$ 25,000,000		$ 25,000,000		$ 25,000,000
Shares issued upon conversion (in shares) | shares		2,455,876		2,455,877
Affiliated Entity [Member] | Entity Affiliated with Dr. Frost | Convertible Debt | 5% Variable Interest Senior Convertible Notes
Related Party Transaction [Line Items]
Principal amount									$ 11,005,000
Interest rate									5.00%
Premium percentage									107.00%
Affiliated Entity [Member] | Entity Affiliated with Dr. Frost | Convertible Debt | 6.75% Variable Interest Senior Convertible Note due 2015
Related Party Transaction [Line Items]
Interest expense													1,094,000
Affiliated Entity [Member] | Frost Real Estate Holdings, LLC
Related Party Transaction [Line Items]
Area of real estate property | ft²								12,390
Operating lease term								5 years
Number of lease extensions | extension								2
Term of lease extensions								5 years
Monthly lease payments, year 1-4																						$ 31,000
Monthly lease payments, year 5 and thereafter																						$ 35,000
Tenant improvement allowance																							$ 220,000
Expenses from transactions with related party												380,000	380,000	$ 380,000
Affiliated Entity [Member] | OPKO Inc.
Related Party Transaction [Line Items]
Investment owned (in shares) | shares							726,036
Amount of transaction																$ 12,788,000
Affiliated Entity [Member] | OPKO Inc. | Opco Convertible Note Receivable, 3 Percent
Related Party Transaction [Line Items]
Loan receivable							$ 5,000,000
Interest rate on receivable							3.00%
Affiliated Entity [Member] | BioCardia, Inc.
Related Party Transaction [Line Items]
Amount of transaction															$ 500,000
Affiliated Entity [Member] | Cocrystal Pharma, Inc.
Related Party Transaction [Line Items]
Amount of transaction															$ 250,000
Son of Company's President and Chief Executive Officer | Douglas Elliman Realty, LLC
Related Party Transaction [Line Items]
Expenses from transactions with related party												$ 640,000	$ 453,000