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Shareholders' Equity - Additional Information (Detail) - USD ($)
12 Months Ended 48 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2017
Feb. 09, 2018
Jul. 20, 2015
Jul. 21, 2014
Accelerated Share Repurchases [Line Items]              
Treasury stock shares (in shares) 8,003,197     10,718,319      
Fair value of common stock repurchased $ 257,683,000     $ 386,322,000      
Stock Repurchase Program, Remaining Authorized Repurchase Amount       $ 238,700,000      
Treasury Stock, Shares, Acquired       10,700,000      
Accelerated Share Repurchase Agreement [Member]              
Accelerated Share Repurchases [Line Items]              
Treasury stock shares (in shares) 209,618 5,408,819 2,384,760 348,460      
Treasury Stock Acquired, Average Cost Per Share $ 36.53 $ 32.35 $ 31.46        
Fair value of common stock repurchased $ 7,700,000 $ 175,000,000.0 $ 75,000,000.0 $ 14,900,000      
Second Accelerated Share Repurchase Agreement [Member]              
Accelerated Share Repurchases [Line Items]              
Treasury stock shares (in shares)       1,076,176      
Fair value of common stock repurchased       $ 50,000,000.0      
Third Accelerated Share Repurchase Agreement [Member]              
Accelerated Share Repurchases [Line Items]              
Stock Repurchase Program, Authorized Amount       75,000,000.0      
Fair value of common stock repurchased       63,800,000      
Maximum [Member]              
Accelerated Share Repurchases [Line Items]              
Stock Repurchase Program, Authorized Amount       $ 100,000,000.0   $ 400,000,000.0 $ 200,000,000.0
Subsequent Event [Member] | Third Accelerated Share Repurchase Program [Member]              
Accelerated Share Repurchases [Line Items]              
Treasury stock shares (in shares)         1,458,713    
Fair value of common stock repurchased         $ 11,200,000    
Share Repurchase Executed Part 2 [Member] | Second Accelerated Share Repurchase Agreement [Member]              
Accelerated Share Repurchases [Line Items]              
Treasury stock shares (in shares)       108,288      
Fair value of common stock repurchased       $ 7,500,000      
Share Repurchase Executed Part 2 [Member] | Subsequent Event [Member] | Third Accelerated Share Repurchase Program [Member]              
Accelerated Share Repurchases [Line Items]              
Treasury stock shares (in shares)         168,227    
Share Repurchase Executed Part 1 [Member] | Second Accelerated Share Repurchase Agreement [Member]              
Accelerated Share Repurchases [Line Items]              
Treasury stock shares (in shares)       967,888      
Fair value of common stock repurchased       $ 42,500,000      
Share Repurchase Executed Part 1 [Member] | Third Accelerated Share Repurchase Agreement [Member]              
Accelerated Share Repurchases [Line Items]              
Treasury stock shares (in shares)       1,290,486