Common Stock Repurchase Programs - Additional Information (Detail) (USD $)
Share data in Millions, unless otherwise specified
3 Months Ended 0 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 16, 2015
Mar. 12, 2015
Oct. 31, 2014
Common Stock [Line Items]          
Repurchases of common stock $ 233,601,000 $ 116,989,000      
Common stock authorized for repurchase         600,000,000
Common stock shares issued 2.7        
Common stock paid 233,600,000        
Common stock purchase       200,000,000  
Accelerated Share Repurchase (ASR) Agreements [Member]          
Common Stock [Line Items]          
Common stock shares issued     2.2    
Common stock paid     200,000,000    
Accelerated Share Repurchase Programs and Open Market Purchases [Member]          
Common Stock [Line Items]          
Repurchases of common stock $ 0