Retirement Plans (Tables)

9 Months Ended

Sep. 30, 2017

Retirement Plans [Abstract]

Components of Net Periodic Benefits Cost

					Other Post-
(in thousands)	Pension Benefits				retirement Benefits
Three months Ended September 30, 2017	2017		2016		2017		2016
Service cost	$	3,769	$	3,611	$	17	$	45
Interest cost		4,056		4,022		155		204
Expected return on plan assets		(9,652)		(8,554)		—		—
Amortization of net loss and prior service costs		1,167		1,426		(128)		53
Net periodic benefit cost (reduction of cost)	$	(660)	$	505	$	44	$	302
Nine months ended September 30, 2017
Service cost	$	11,612	$	10,487	$	112	$	119
Interest cost		12,470		13,033		514		613
Expected return on plan assets		(27,978)		(25,999)		—		—
Amortization of net loss and prior service costs		4,368		4,320		(224)		75
Net periodic benefit cost	$	472	$	1,841	$	402	$	807