Quarterly report pursuant to Section 13 or 15(d)

Stock-based Compensation - Additional Information (Detail)

v2.4.0.6
Stock-based Compensation - Additional Information (Detail) (USD $)
3 Months Ended
Mar. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Options granted in period 855,058
Exercise price of options granted $ 145.58
Vesting period 3 years
Expected volatility, minimum 27.00%
Expected volatility, maximum 31.00%
Weighted average, expected volatility 30.00%
Expected dividend yield 2.50%
Risk-free interest rate, at ten years 2.10%
Risk-free interest rate, at six months 0.10%
Weighted average fair value of options granted $ 33.43
Performance based period 3 years
Performance based adjustment 25.00%
Restricted Stock Units
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Fair value of restricted stock units at the grant date $ 145.58
Restricted Stock
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Restricted stock units granted in period 5,500
Fair value of restricted stock units at the grant date $ 141.77
Share based compensation expected vesting period assuming grantees remain employed 2016
Minimum
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Expected term 5 years 219 days
Performance based adjustment 0.00%
Maximum
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Expected term 7 years 183 days
Performance-Based | Restricted Stock Units
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Restricted stock units granted in period 191,788
Share based compensation vesting period 3 years
Performance-Based | Minimum | Restricted Stock Units
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Range of possible awards 0.00%
Performance-Based | Maximum | Restricted Stock Units
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Range of possible awards 200.00%
Nonperformance Based | Restricted Stock Units
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Restricted stock units granted in period 4,345
Board Of Director Grants
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Stock options granted period of time options become exercisable 1 year