ONEOK INC /NEW/ | 2013 | FY | 3

Obligations and Funded Status - The following tables set forth our pension and postretirement benefit plans benefit obligations and fair value of plan assets for the periods indicated:
 
 
Pension Benefits
 
Postretirement Benefits
 
 
December 31,
 
December 31,
 
 
2013
 
2012
 
2013
 
2012
Change in Benefit Obligation
 
(Thousands of dollars)
Benefit obligation, beginning of period
 
$
1,313,560

 
$
1,215,932

 
$
299,172

 
$
286,044

Service cost
 
22,968

 
21,301

 
4,612

 
4,960

Interest cost
 
54,449

 
59,237

 
11,713

 
13,893

Plan participants’ contributions
 
—

 
—

 
4,293

 
5,851

Actuarial loss (gain)
 
(110,552
)
 
105,732

 
(29,460
)
 
9,935

Benefits paid
 
(58,976
)
 
(88,642
)
 
(18,411
)
 
(21,380
)
Plan amendment
 
—

 
—

 
17,228

 
(131
)
Benefit obligation, end of period
 
1,221,449

 
1,313,560

 
289,147

 
299,172

 
 
 
 
 
 
 
 
 
Change in Plan Assets
 
 

 
 

 
 

 
 

Fair value of plan assets, beginning of period
 
995,264

 
902,235

 
148,162

 
124,163

Actual return on plan assets
 
176,889

 
90,026

 
27,483

 
14,273

Employer contributions
 
—

 
91,881

 
866

 
10,728

Benefits paid
 
(59,404
)
 
(88,878
)
 
(876
)
 
(1,002
)
Fair value of assets, end of period
 
1,112,749

 
995,264

 
175,635

 
148,162

Balance at December 31
 
$
(108,700
)
 
$
(318,296
)
 
$
(113,512
)
 
$
(151,010
)
 
 
 
 
 
 
 
 
 
Current liabilities
 
$
(5,457
)
 
$
(4,695
)
 
$
—

 
$
—

Noncurrent liabilities
 
(103,243
)
 
(313,601
)
 
(113,512
)
 
(151,010
)
Balance at December 31
 
$
(108,700
)
 
$
(318,296
)
 
$
(113,512
)
 
$
(151,010
)

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