Employee Benefit Plans

We sponsor two union pension plans for certain union employees and a pension plan primarily for salaried employees, a postretirement benefit plan for selected employees and a defined contribution plan. The following tables present our consolidated net periodic benefit costs related to the pension and postretirement benefit plans for the three months ended March 31, 2013 and 2014 (in thousands):



	Three Months Ended						Three Months Ended
	March 31, 2013						March 31, 2014
	Pension Benefits			Other Post- Retirement Benefits			Pension Benefits			Other Post- Retirement Benefits
Components of net periodic benefit costs:
Service cost	$	3,576		$	77		$	3,352		$	67
Interest cost	1,350			115			1,659			114
Expected return on plan assets	(1,470		)	—			(1,697		)	—
Amortization of prior service cost (credit)⁽¹⁾	77			(928		)	33			(928		)
Amortization of actuarial loss⁽¹⁾	1,022			308			629			195
Net periodic benefit cost (credit)	$	4,555		$	(428	)	$	3,976		$	(552	)

(1) These amounts are included in our Consolidated Statements of Comprehensive Income and Consolidated Statements of Cash Flows as changes in employee benefit plan assets and benefit obligations.