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Information Concerning Guarantor and Non-Guarantor Subsidiaries - Additional Information (Detail)
$ in Millions
6 Months Ended
Jun. 30, 2015
USD ($)
Entity
Dec. 31, 2014
USD ($)
Condensed Financial Statements, Captions [Line Items]    
Number of wholly owned subsidiaries | Entity 4  
Ownership percentage in subsidiaries 100.00%  
Guarantors [Member]    
Condensed Financial Statements, Captions [Line Items]    
Number of wholly owned subsidiaries | Entity 4  
$350 Million Senior Notes at 5% Interest [Member]    
Condensed Financial Statements, Captions [Line Items]    
Interest rate of Senior Notes 5.00% 5.00%
Senior notes, principal amount $ 350 $ 350
$400 Million 5% Senior Notes [Member]    
Condensed Financial Statements, Captions [Line Items]    
Interest rate of Senior Notes 5.00%  
Senior notes, principal amount $ 400