VALERO ENERGY CORP/TX | 2013 | FY | 3

The changes in benefit obligation related to all of our defined benefit plans, the changes in fair value of plan assets(a), and the funded status of our defined benefit plans as of and for the years ended were as follows (in millions):
 
Pension Plans
 
Other Postretirement
Benefit Plans
 
December 31,
 
December 31,
 
2013
 
2012
 
2013
 
2012
Changes in benefit obligation:
 
 
 
 
 
 
 
Benefit obligation as of beginning of year
$
2,307

 
$
1,881

 
$
436

 
$
438

Service cost
137

 
140

 
12

 
12

Interest cost
86

 
93

 
18

 
21

Participant contributions
—

 
—

 
15

 
14

Plan amendments
(274
)
 
9

 
(43
)
 
—

Curtailment gain
(6
)
 
(16
)
 
—

 
—

Benefits paid
(170
)
 
(90
)
 
(37
)
 
(35
)
Actuarial (gain) loss
(169
)
 
289

 
(77
)
 
(17
)
Other
3

 
1

 
—

 
3

Benefit obligation as of end of year
$
1,914

 
$
2,307

 
$
324

 
$
436

 
 
 
 
 
 
 
 
Changes in plan assets(a):
 
 
 
 
 
 
 
Fair value of plan assets as of beginning of year
$
1,729

 
$
1,487

 
$
—

 
$
—

Actual return on plan assets
306

 
167

 
—

 
—

Valero contributions
41

 
164

 
19

 
19

Participant contributions
—

 
—

 
15

 
14

Benefits paid
(170
)
 
(90
)
 
(37
)
 
(35
)
Other
3

 
1

 
3

 
2

Fair value of plan assets as of end of year
$
1,909

 
$
1,729

 
$
—

 
$
—

 
 
 
 
 
 
 
 
Reconciliation of funded status(a):
 
 
 
 
 
 
 
Fair value of plan assets as of end of year
$
1,909

 
$
1,729

 
$
—

 
$
—

Less benefit obligation as of end of year
1,914

 
2,307

 
324

 
436

Funded status as of end of year
$
(5
)
 
$
(578
)
 
$
(324
)
 
$
(436
)
 
 
 
 
 
 
 
 
Accumulated benefit obligation
$
1,811

 
$
1,857

 
n/a

 
n/a


___________________________ 
(a) 
Plan assets include only the assets associated with pension plans subject to legal minimum funding standards. Plan assets associated with U.S. nonqualified pension plans are not included here because they are not protected from our creditors and therefore cannot be reflected as a reduction from our obligations under the pension plans. As a result, the reconciliation of funded status does not reflect the effect of plan assets that exist for all of our defined benefit plans. See Note 20 for the assets associated with certain U.S. nonqualified pension plans.

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