Annual report pursuant to Section 13 and 15(d)

Long-Term Debt (Narrative) (Details)

v2.4.0.6
Long-Term Debt (Narrative) (Details) (USD $)
9 Months Ended 12 Months Ended 12 Months Ended
Sep. 30, 2011
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Dec. 31, 2011
Tranche A Notes [Member]
Dec. 31, 2011
Tranche B Notes [Member]
Dec. 31, 2011
Letter Of Credit [Member]
Dec. 31, 2010
Letter Of Credit [Member]
Dec. 31, 2011
Sweep Program [Member]
Aug. 10, 2011
Five-Year Senior Unsecured Revolving Credit Facility [Member]
Dec. 31, 2010
Line Of Credit [Member]
Dec. 31, 2010
Senior Notes [Member]
Dec. 31, 2011
Maximum [Member]
Dec. 31, 2011
Minimum [Member]
Debt Instrument [Line Items]                            
Unsecured senior note outstanding   $ 262,900,000                        
Periodic principal payments   35,700,000                        
Fixed interest rate, minimum   4.00%                        
Fixed interest rate, maximum   5.85%                        
Effective average interest rate   5.17% 5.54%                      
Senior notes, noncurrent   95,000,000     50,000,000 45,000,000                
Fixed interest rate         4.00% 4.79%                
Maximum borrowing capacity   300,000,000         150,000,000   20,000,000          
Current borrowing capacity                   200,000,000        
Minimum increments under the additional borrowings   25,000,000                        
Credit facility interest At our option, revolving loans under the facility bear interest at either: (a) the Applicable Margin Percentage for Base Rate Loans plus the higher of Wells Fargo's prime rate, the federal funds rate plus 0.5% per annum, or the one month LIBOR Rate plus 1.0% per annum; (b) the LIBOR Rate plus the Applicable Margin Percentage for LIBOR Loans; or (c) the LIBOR Market Index Rate ("LIBOR Index Rate") plus the Applicable Margin Percentage for LIBOR Market Index Loans                          
Applicable margin interest on credit facility, low end   1.00%                        
Applicable margin interest on credit facility, high end   1.875%                        
Margin interest during period   1.125%                        
Decreases in marginal interest during period   0.50%                        
LIBOR rate   1.00%                        
Line of credit, outstanding   0 66,230,000       49,900,000 49,600,000     66,200,000      
Proceeds from issuance of long-term debt   96,010,000 0 0               95,000,000    
Senior notes, issuance date                       January 3, 2011    
Line of credit fee   1.125%                        
Commitment fee percentage   0.20%                     0.30% 0.175%
Facing fee on outstanding amount of letter of credit   0.125%                        
Minimum amount of dividends payable to shareholder as per credit agreement   20,000,000                        
Percentage of preceding year net income payable as dividend   25.00%                        
Collateralized property and equipment book value   $ 9,200,000