Benefit Plans and Other Postretirement Benefits (Tables)

3 Months Ended

Mar. 31, 2013

Benefit Plans and Other Postretirement Benefits

Schedule of components of net pension expense

	Pension Benefits						Other Postretirement Benefits
	Three months ended March 31,
	2013			2012			2013		2012
Service cost	$	2,112		$	1,945		$	40	$	45
Interest cost	5,207			5,527			127		169
Expected return on plan assets	(6,203		)	(6,236		)	—		—
Amortization of transition obligation	(27		)	(27		)	—		16
Amortization of prior service cost	495			541			—		—
Amortization of net actuarial losses	5,905			4,553			193		242
Net pension expense	$	7,489		$	6,303		$	360	$	472