Employee Benefit Plans

6 Months Ended

Jun. 30, 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 tables present our consolidated net periodic benefit costs related to these plans for the three and six months ended June 30, 2011 and 2012 (in thousands):

		Three Months Ended						Three Months Ended
		June 30, 2011						June 30, 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		$	137
Interest cost		950			260			1,204			258
Expected return on plan assets		(1,022	)		—			(1,176	)		—
Amortization of prior service cost (credit)		77			(213	)		77			(211	)
Amortization of actuarial loss		151			62			826			161
Net periodic benefit cost	$	2,141		$	200		$	4,121		$	345

		Six Months Ended						Six Months Ended
		June 30, 2011						June 30, 2012
					Other Post-						Other Post-
		Pension			Retirement			Pension			Retirement
		Benefits			Benefits			Benefits			Benefits
Components of net periodic benefit costs:
Service cost	$	3,970		$	182		$	6,380		$	275
Interest cost		1,899			519			2,407			515
Expected return on plan assets		(2,043	)		—			(2,352	)		—
Amortization of prior service cost (credit)		154			(426	)		154			(424	)
Amortization of actuarial loss		302			125			1,653			322
Net periodic benefit cost	$	4,282		$	400		$	8,242		$	688

     Net periodic benefit costs for the pension plans increased in 2012 primarily due to a decrease in the discount rate at December 31, 2011.

     Contributions estimated to be paid into the plans in 2012 are $13.3 million and $0.3 million for the pension and other postretirement benefit plans, respectively.