Pension and other postretirement benefits (Tables)

9 Months Ended

Sep. 30, 2012

Schedule of net benefit cost of pension and postretirement benefit plans

Net benefit cost of pension and postretirement benefit plans consisted of the following:

	Pension Three Months Ended						Postretirement Benefits Three Months Ended					Pension Nine Months Ended						Postretirement Benefits Nine Months Ended
	September 30, 2012			September 25, 2011			September 30, 2012		September 25, 2011			September 30, 2012			September 25, 2011			September 30, 2012		September 25, 2011
									(Dollars in thousands)
Service cost	$	696		$	531		$	159	$	(37	)	$	2,085		$	1,723		$	475	$	359
Interest cost		4,115			4,387			473		441			12,366			12,973			1,419		1,541
Expected return on Plan assets		(5,043	)		(5,160	)		—		—			(15,128	)		(15,003	)		—		—
Net amortization and deferral		1,604			987			123		(172	)		4,814			3,018			368		(34	)
Settlement charge		—			—			—		—			(124	)		—			—		—
Curtailment charge		—			—			—		—			111			—			—		—
Net benefit cost	$	1,372		$	745		$	755	$	232		$	4,124		$	2,711		$	2,262	$	1,866