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Employee Benefit Plans
 3 Months Ended
Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]  
Employee Benefit Plans
Employee Benefit Plans

Net periodic benefit income for the pension plans included the following components for the three months ended March 31:
 
 
Pension Benefits
 
2017
 
2016
 
(in thousands)
Service cost
$
2,157

 
$
2,027

Interest cost
24,132

 
26,091

Expected return on plan assets
(39,733
)
 
(39,138
)
Amortization of prior service credit
(88
)
 
(108
)
Amortization of actuarial loss
9,485

 
7,795

Net periodic benefit income
$
(4,047
)
 
$
(3,333
)


Pension benefits also include amounts related to a supplemental retirement plan. During the three months ended March 31, 2017, the Company made a $38.7 million contribution to the pension plan.