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Stock-Based Compensation (Details Textual)			1 Months Ended	3 Months Ended	12 Months Ended
Stock-Based Compensation (Details Textual)	Feb. 11, 2019 USD ($) Item $ / shares shares	May 05, 2015	Aug. 31, 2018 USD ($) shares	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	May 07, 2018 shares	Aug. 31, 2017
Stock-Based Compensation (Textual)
Stock-based compensation					$ 1,102,000	$ 4,523,000
Total intrinsic value of options exercised					800,000	800,000
Class B common stock issued for GRE deferred stock units				$ 1,886,000	$ (5,584,000)	1,886,000
Option awards vest services contractual term					3 years
Option awards vest contractual term					10 years
Class B common stock with aggregate cost						800
Proceeds from Stock Options Exercised					$ 1,407,000
GREI [Member]
Stock-Based Compensation (Textual)
Ownership interest of company								4.00%
Vesting of deferred stock units					$ 100,000
GES [Member]
Stock-Based Compensation (Textual)
Ownership interest of company								4.50%
Officers and employees [Member]
Stock-Based Compensation (Textual)
Ownership interest of company		3.90%
Option awards vest contractual term		3 years
Restricted Stock [Member]
Stock-Based Compensation (Textual)
Option awards vest services contractual term					3 years
Restricted Stock Granted [Member]
Stock-Based Compensation (Textual)
Total grant date fair value of shares vested					$ 400,000	400,000
Stock-based compensation					1,000,000	3,400,000
Stock options [Member]
Stock-Based Compensation (Textual)
Stock-based compensation					$ 100,000
Other Subsidiary Equity [Member]
Stock-Based Compensation (Textual)
Stock-based compensation						$ 1,100,000
Common Class B [Member]
Stock-Based Compensation (Textual)
Class B common stock issued for GRE deferred stock units, Shares \| shares						310
Class B common stock issued for GRE deferred stock units						$ 3,000
Class B common stock with aggregate cost			$ 800,000
Acquired shares \| shares			128,865
Common Class B [Member] \| GRE [Member]
Stock-Based Compensation (Textual)
Class B common stock issued for GRE deferred stock units, Shares \| shares			310,467
Class B common stock issued for GRE deferred stock units			$ 1,900,000
Common Class B [Member] \| Howard Jonas [Member]
Stock-Based Compensation (Textual)
Exercise price \| $ / shares	$ 8.05
Cash bonus	$ 300,000
Acquired shares \| shares	126,176
Number of annual installments in which options will vest \| Item	3
Common Class B [Member] \| Restricted Stock [Member]
Stock-Based Compensation (Textual)
Total unrecognized compensation cost					$ 1,000,000
Period of unrecognized compensation cost expected to be recognized					1 year 4 months 24 days
2011 Stock Option and Incentive Plan [Member]
Stock-Based Compensation (Textual)
Shares available for future grants, Shares \| shares					503,000
2011 Stock Option and Incentive Plan [Member] \| Common Class B [Member]
Stock-Based Compensation (Textual)
Shares available for future grants, Shares \| shares							372,000
Common stock reserved for future issuance \| shares					2,700,000		974,199