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Revolving Line of Credit (Detail)
Nov. 17, 2017
USD ($)
Mar. 31, 2018
USD ($)
Line of Credit Facility [Line Items]    
Unsecured revolving line of credit $ 600,000,000  
Revolving credit facility, expiration date Dec. 30, 2019  
Credit facility restrictive covenant, minimum fixed charge ratio 2.5  
Credit facility restrictive covenant, maximum consolidated leverage ratio 3.0  
Credit facility restrictive covenant, maximum consolidated leverage ratio step up 3.5  
Borrowings outstanding   $ 460,000,000
Interest rate of borrowings outstanding   2.973%
Long-term Debt    
Line of Credit Facility [Line Items]    
Borrowings outstanding   $ 400,000,000
Federal Fund Rate    
Line of Credit Facility [Line Items]    
Debt instrument basis spread on variable rate 0.50%  
Libor    
Line of Credit Facility [Line Items]    
Debt instrument basis spread on variable rate 1.00%  
Libor | Minimum    
Line of Credit Facility [Line Items]    
Debt instrument basis spread on variable rate 1.00%  
Libor | Maximum    
Line of Credit Facility [Line Items]    
Debt instrument basis spread on variable rate 1.875%  
Base Rate | Minimum    
Line of Credit Facility [Line Items]    
Debt instrument basis spread on variable rate 0.00%  
Base Rate | Maximum    
Line of Credit Facility [Line Items]    
Debt instrument basis spread on variable rate 0.875%