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Stock-Based Compensation - Additional Information (Detail) - shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Incentive plan, shares available for grant 6,872,282 8,458,593 4,368,753 6,804,452
Restricted stock units outstanding 105,679,000 98,039,000 85,717,000  
2011 Plan Amendment [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Incentive plan, shares available for grant   6,300,000.0    
Performance Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Contractual period 3 years      
Executive Performance Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Settlement of performance shares   211,000 159,000  
Minimum [Member] | Equity Option [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Contract period 7 years      
Minimum [Member] | Performance Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance shares target distribution 0 0 0  
Maximum [Member] | Equity Option [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Contract period 10 years      
Maximum [Member] | Performance Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance shares target distribution 359,000 359,000 295,000  
Employee [Member] | Restricted Stock [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period 5 years      
Director [Member] | Restricted Stock Units (RSUs) [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period 6 months