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Subsequent Events - Additional Information (Detail) - USD ($)
 1 Months Ended 12 Months Ended
Jan. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Subsequent Event [Line Items]        
Stock repurchase program, authorized amount     $ 500,000,000  
Repurchase of stock, value   $ 200,304,000 $ 146,331,000 $ 299,949,000
Subsequent Event        
Subsequent Event [Line Items]        
Cash Dividends payable, amount per share $ 0.09      
Cash Dividends payable, date to be paid Mar. 23, 2018      
Cash Dividends payable, record date Feb. 23, 2018      
Stock repurchase program, authorized amount $ 1,500,000,000      
Repurchase of stock, value $ 750,000,000