v2.4.0.6
Stock-based compensation Stock-based compensation (Tables)
 12 Months Ended
Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Components of stock-based compensation expense recognized in the Consolidated Statements of Income
The following table reflects the components of stock-based compensation expense recognized in our Consolidated Statements of Income for the years ended December 31, 2012, 2011 and 2010 (in millions):
 
2012
 
2011
 
2010
Stock options
$
59

 
$
85

 
$
124

RSUs
186

 
188

 
182

Performance units
117

 
68

 
47

Total stock-based compensation expense, pretax
362

 
341

 
353

Tax benefit from stock-based compensation expense
(134
)
 
(124
)
 
(120
)
Total stock-based compensation expense, net of tax
$
228

 
$
217

 
$
233
Weighted average assumptions used and the resulting weighted average grant date fair value of employee stock options
The weighted-average assumptions used in the option valuation model and the resulting weighted-average estimated grant date fair values of stock options were as follows for the years ended December 31, 2012, 2011 and 2010:
 
2012
 
2011
 
2010
Closing price of our common stock on grant date
$
74.56

 
$
54.66

 
$
58.32

Expected volatility
22.2
%
 
23.5
%
 
28.0
%
Expected life (in years)
8.1

 
5.9

 
6.6

Risk-free interest rate
1.6
%
 
2.5
%
 
3.2
%
Expected dividend yield
2.1
%
 
2.0
%
 
0
%
Fair value of stock options granted
$
14.65

 
$
11.39

 
$
20.97
Stock options information
The following summarizes select information regarding our stock options during the year ended December 31, 2012:
 
Options
(in millions)
 
Weighted-
average
exercise price
 
Weighted-
average
remaining
contractual
life (years)
 
Aggregate
intrinsic
value
(in millions)
Balance unexercised at December 31, 2011
34.2

 
$
59.11

 
 
 
 
Granted
0.1

 
$
74.56

 
 
 
 
Exercised
(20.9
)
 
$
60.67

 
 
 
 
Expired/forfeited
(1.1
)
 
$
63.97

 
 
 
 
Balance unexercised at December 31, 2012
12.3

 
$
56.09

 
4.9
 
$
371

Vested or expected to vest at December 31, 2012
12.2

 
$
56.10

 
4.9
 
$
367

Exercisable at December 31, 2012
6.3

 
$
56.59

 
3.1
 
$
187
Restricted stock units Information
The following summarizes select information regarding our RSUs during the year ended December 31, 2012:
 
Units
(in millions)
 
Weighted-average
grant date
fair value
Balance nonvested at December 31, 2011
9.0

 
$
52.64

Granted
3.9

 
$
72.99

Vested
(2.8
)
 
$
50.64

Forfeited
(0.7
)
 
$
58.38

Balance nonvested at December 31, 2012
9.4

 
$
61.14
Weighted average assumptions used and the resulting weighted average grant date fair value of performance units
The weighted-average assumptions used in these models and the resulting weighted-average grant date fair values of our performance units were as follows for the years ended December 31, 2012, 2011 and 2010:
 
2012
 
2011
 
2010
Closing price of our common stock on grant date
$
68.75

 
$
51.67

 
$
56.90

Volatility
22.9
%
 
32.8
%
 
34.7
%
Risk-free interest rate
0.5
%
 
1.2
%
 
1.3
%
Expected dividend yield
2.2
%
 
0.1
%
 
0
%
Fair value of unit
$
78.21

 
$
49.50

 
$
62.06