Employee Benefit Plans

3 Months Ended

Mar. 31, 2012

Employee Benefit Plans [Abstract]

Employee Benefit Plans

5. Employee Benefit Plans

     We sponsor two union pension plans for certain employees and a pension plan primarily for salaried employees, a postretirement benefit plan for selected employees and a defined contribution plan. The following table presents our consolidated net periodic benefit costs related to these plans during the three months ended March 31, 2011 and 2012 (in thousands):

		Three Months Ended						Three Months Ended
		March 31, 2011						March 31, 2012
					Other Post-						Other Post-
		Pension			Retirement			Pension			Retirement
		Benefits			Benefits			Benefits			Benefits
Components of net periodic benefit costs:
Service cost	$	1,985		$	91		$	3,190		$	138
Interest cost		949			259			1,203			257
Expected return on plan assets		(1,021	)		—			(1,176	)		—
Amortization of prior service cost (credit)		77			(213	)		77			(213	)
Amortization of actuarial loss		151			63			827			161
Net periodic benefit cost	$	2,141		$	200		$	4,121		$	343

     Net periodic benefit costs for the pension plans increased approximately $2.0 million in first quarter 2012 primarily due to decreases in the discount rate at December 31, 2011.

     Contributions estimated to be paid into the plans in 2012 are $12.7 million and $0.6 million for the pension and other postretirement benefit plans, respectively.