Benefit Plans and Other Postretirement Benefits (Tables)

6 Months Ended

Jun. 30, 2013

Benefit Plans and Other Postretirement Benefits

Schedule of components of net pension expense

	Pension Benefits						Other Postretirement Benefits
	Three months ended June 30,
	2013			2012			2013		2012
Service cost	$	2,103		$	1,939		$	40	$	45
Interest cost	5,107			5,426			127		169
Expected return on plan assets	(6,071		)	(6,083		)	—		—
Amortization of transition obligation	(27		)	(27		)	—		16
Amortization of prior service cost	485			534			—		—
Amortization of net actuarial losses	5,897			4,555			193		242
Net pension expense	$	7,494		$	6,344		$	360	$	472

	Pension Benefits						Other Postretirement Benefits
	Six months ended June 30,
	2013			2012			2013		2012
Service cost	$	4,215		$	3,884		$	80	$	90
Interest cost	10,314			10,953			255		339
Expected return on plan assets	(12,274		)	(12,319		)	—		—
Amortization of transition obligation	(54		)	(54		)	—		31
Amortization of prior service cost	980			1,075			—		—
Amortization of net actuarial losses	11,802			9,108			385		483
Net pension expense	$	14,983		$	12,647		$	720	$	943