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EMPLOYEE BENEFIT PLANS
 3 Months Ended
Mar. 31, 2012
Compensation and Retirement Disclosure [Abstract]  
EMPLOYEE BENEFIT PLANS
EMPLOYEE BENEFIT PLANS

Net periodic benefit costs recognized included the following components for the three months ended March 31 (in millions): 
 
Qualified

Nonqualified

Postretirement Medical
 
2012
 
2011
 
2012
 
2011
 
2012
 
2011
Service cost
$
9.6

 
$
9.0

 
$
0.2

 
$
0.2

 
$
1.2

 
$
1.5

Interest cost
18.2

 
18.3

 
0.5

 
0.6

 
1.4

 
1.8

Expected return on assets
(23.3
)
 
(22.1
)
 
—

 
—

 
—

 
—

Amortization of prior service cost
(0.2
)
 
(0.2
)
 
—

 
—

 
0.1

 
0.1

Recognized actuarial loss
9.9

 
6.1

 
0.2

 
0.1

 
(0.1
)
 
0.3

Net periodic benefit costs
$
14.2

 
$
11.1

 
$
0.9

 
$
0.9

 
$
2.6

 
$
3.7