Annual report pursuant to Section 13 and 15(d)

Debt (Lines-Of-Credit and Notes Payable, Narrative) (Details)

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Debt (Lines-Of-Credit and Notes Payable, Narrative) (Details) - USD ($)
12 Months Ended
Apr. 17, 2018
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Mar. 31, 2013
Debt Instrument [Line Items]          
Proceeds from borrowings under line-of-credit facilities and notes payable   $ 51,736,000 $ 36,426,000 $ 45,243,000  
Availablility of line of credits/credit facilities   193,300,000      
2013 Notes Payable [Member]          
Debt Instrument [Line Items]          
Debt instrument, face amount         $ 75,000,000
Non-revolving term loan   28,125,000 46,500,000    
NBA Line Of Credit [Member]          
Debt Instrument [Line Items]          
Maximum borrowing capacity   20,000,000      
Non-revolving term loan     5,089,000    
NBA Eilan Loan [Member]          
Debt Instrument [Line Items]          
Maximum borrowing capacity $ 27,500,000        
Proceeds from borrowings under line-of-credit facilities and notes payable 24,300,000        
Fund for improvement costs 1,700,000        
Availablility of line of credits/credit facilities $ 1,500,000        
Non-revolving term loan   25,603,000      
NBA Eilan Loan [Member] | LIBOR [Member] | Minimum [Member]          
Debt Instrument [Line Items]          
Basis spread on rate 3.25%        
Effective rate 4.75%        
Fifth Third Syndicated Line-of-Credit And Fifth Third Syndicated Term Loan [Member]          
Debt Instrument [Line Items]          
Debt instrument, face amount   25,000,000      
Maximum borrowing capacity       $ 100,000,000  
Non-revolving term loan   77,500,000      
Fifth Third Syndicated LOC [Member]          
Debt Instrument [Line Items]          
Maximum borrowing capacity   75,000,000      
Non-revolving term loan   $ 55,000,000 $ 20,000,000    
Fifth Third Syndicated LOC [Member] | LIBOR [Member] | Minimum [Member]          
Debt Instrument [Line Items]          
Basis spread on rate   2.75%      
Fifth Third Syndicated LOC [Member] | LIBOR [Member] | Maximum [Member]          
Debt Instrument [Line Items]          
Basis spread on rate   3.75%      
NBA Receivables Facility [Member]          
Debt Instrument [Line Items]          
Maximum borrowing capacity   $ 70,000,000      
NBA Receivables Facility [Member] | Minimum [Member]          
Debt Instrument [Line Items]          
Effective rate   3.50%