Retirement Plans and Other Post-Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2018

Compensation And Retirement Disclosure [Abstract]

Schedule of Net Periodic Costs of Pension and Post Retirement Medical Benefit Plans

The following tables provide information with respect to the net periodic costs of our pension and post-retirement medical benefit plans.

	Three months ended March 31
In thousands	2018			2017
Pension Benefits
Service cost	$	2,859		$	2,721
Interest cost		5,589			5,907
Expected return on plan assets		(10,839	)		(10,831	)
Amortization of prior service    cost		780			704
Amortization of unrecognized    loss		3,390			2,822
Total net periodic benefit cost	$	1,779		$	1,323
Other Benefits
Service cost	$	307		$	295
Interest cost		451			485
Amortization of prior    service credit		(45	)		(45	)
Amortization of    actuarial gain		(73	)		(143	)
Total net periodic    benefit cost	$	640		$	592