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Long-Term Debt (5.625% Senior Notes due 2023) - Additional Information (Detail) - 5.625% Senior Notes Due 2023 [Member] - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Sep. 21, 2015
Feb. 11, 2015
Debt Instrument [Line Items]        
Issued Senior Notes     $ 275,000,000 $ 375,000,000
Debt instrument interest rate 5.625% 5.625% 5.625% 5.625%
Senior Notes $ 650,000,000 $ 650,000,000 $ 650,000,000  
Debt instrument maturity date Feb. 15, 2023