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DEBT (Details)
1 Months Ended 3 Months Ended 8 Months Ended 9 Months Ended
Apr. 27, 2017
May 02, 2016
May 09, 2011
May 31, 2015
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2017
USD ($)
Apr. 28, 2017
USD ($)
Mar. 31, 2017
USD ($)
Debt Disclosure [Line Items]                  
Initiation date of credit agreement     May 09, 2011            
Amendment date of Credit Agreement   Apr. 28, 2017              
Credit facility expiration date             May 09, 2020    
Commitment fee percentage             0.37%    
Proceeds from line of credit         $ 8,000,000        
Repayment of line of credit         8,000,000        
Outstanding borrowings under line of credit         $ 0 $ 0 $ 0   $ 0
Maximum ratio of funded debt to EBITDA 3         3.25      
Minimum required liquid funds             $ 300,000,000.0    
Line Of Credit Facility Interest Rate Spread Below The Banks Announced Prime Rate [Member]                  
Debt Disclosure [Line Items]                  
Spread for interest rate             1.20%    
Line Of Credit Facility Interest Rate Spread Above A Daily One Month LIBOR Rate [Member]                  
Debt Disclosure [Line Items]                  
Spread for interest rate             1.40%    
Senior Notes [Member] | 5.50% Senior Notes [Member]                  
Debt Disclosure [Line Items]                  
Principal amount of debt issued       $ 500,000,000.0          
Stated interest rate of debt instrument       5.50% 5.50% 5.50% 5.50%    
Proceeds from issuance of senior notes, net of issuance costs       $ 488,400,000          
Debt issuance costs       $ 11,600,000          
Debt redemption percentage price, Specified Price       105.50%          
Repurchase price, percentage of principal amount       101.00%          
Minimum [Member] | Senior Notes [Member] | 5.50% Senior Notes [Member]                  
Debt Disclosure [Line Items]                  
Debt redemption notice period       30 days          
Maximum [Member] | Senior Notes [Member] | 5.50% Senior Notes [Member]                  
Debt Disclosure [Line Items]                  
Debt redemption notice period       60 days          
Percentage of debt redeemed       35.00%          
Level 2 [Member] | Fair Value [Member] | Senior Notes [Member] | 5.50% Senior Notes [Member]                  
Debt Disclosure [Line Items]                  
Long-term debt, 5.50% Senior Notes         $ 520,425,000 $ 520,425,000 $ 520,425,000   505,150,000
Level 2 [Member] | Carrying Value [Member] | Senior Notes [Member] | 5.50% Senior Notes [Member]                  
Debt Disclosure [Line Items]                  
Long-term debt, 5.50% Senior Notes         $ 492,146,000 $ 492,146,000 $ 492,146,000   $ 491,059,000
Revolving Credit Facility [Member]                  
Debt Disclosure [Line Items]                  
Maximum borrowing capacity of unsecured revolving credit facility               $ 100,000,000.0