Annual report pursuant to Section 13 and 15(d)

Long-Term Debt (Narrative) (Details)

v2.4.0.6
Long-Term Debt (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Debt Instrument [Line Items]    
Senior Notes $ 227,143,000 $ 262,857,000
Maximum borrowing capacity 300,000,000  
Minimum increments under the additional borrowings 25,000,000  
Interest Rate Spread added to LIBOR Rate 1.00%  
Interest Rate Spread added to Federal Funds Rate 0.50%  
Line of credit, outstanding 10,000,000 0
Facing fee on outstanding amount of letter of credit 0.125%  
Minimum amount of dividends payable to shareholder as per credit agreement 20.0  
Percentage of preceding year net income payable as dividend 25.00%  
Collateralized property and equipment book value 7,600,000  
Letter Of Credit [Member]
   
Debt Instrument [Line Items]    
Maximum borrowing capacity 150,000,000  
Line of credit, outstanding 52,400,000 49,900,000
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  
Applicable Margin Interest On Credit Facility Low End 1.00%  
Applicable Margin Interest On Credit Facility High End 1.875%  
Interest Rate Spread added to LIBOR Rate 1.125% 1.125%
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 5.07% 5.17%
Maximum [Member]
   
Debt Instrument [Line Items]    
Interest Rate Spread added to LIBOR Rate 1.125%  
Letter of credit fee 1.125%  
Commitment fee percentage 0.20%  
Line Of Credit Facility Commitment Stated Fee Percentage 0.30%  
Minimum [Member]
   
Debt Instrument [Line Items]    
Interest Rate Spread added to LIBOR Rate 1.00%  
Letter of credit fee 1.00%  
Commitment fee percentage 0.175%  
Line Of Credit Facility Commitment Stated Fee Percentage 0.175%