Quarterly report pursuant to Section 13 or 15(d)

Long-Term Debt (Narrative) (Details)

v2.4.0.8
Long-Term Debt (Narrative) (Details) (USD $)
6 Months Ended 12 Months Ended
Jun. 30, 2014
Dec. 31, 2013
Debt Instrument [Line Items]    
Senior Notes $ 155,714,000 $ 191,429,000
Interest Rate Spread added to LIBOR Rate 1.00%  
Applicable Margin Percentage, Interest Rate added to federal funds rate 0.50%  
Line of Credit Facility, Amount Outstanding 44,000,000 0
Letter Of Credit [Member]
   
Debt Instrument [Line Items]    
Maximum borrowing capacity 150,000,000  
Line of Credit Facility, Amount Outstanding 64,600,000 57,700,000
Sweep Program [Member]
   
Debt Instrument [Line Items]    
Maximum borrowing capacity 20,000,000  
Five Year Senior Unsecured Revolving Credit Facility [Member]
   
Debt Instrument [Line Items]    
Current borrowing capacity 200,000,000  
Line Of Credit, Additional Capacity 100,000,000  
Minimum increments under the additional borrowings 25,000,000  
Interest Rate Spread added to LIBOR Rate 1.00% 1.00%
Senior Notes [Member]
   
Debt Instrument [Line Items]    
Periodic principal payments $ 35,700,000  
Fixed interest rate, minimum 4.00%  
Fixed interest rate, maximum 5.85%  
Effective average interest rate 4.87% 4.99%
Maximum [Member]
   
Debt Instrument [Line Items]    
Interest Rate Spread added to LIBOR Rate 1.875%  
Minimum [Member]
   
Debt Instrument [Line Items]    
Interest Rate Spread added to LIBOR Rate 1.00%