Retirement Plans (Tables)

6 Months Ended

Jun. 30, 2018

Retirement Plans [Abstract]

Components of Net Periodic Benefits Cost

					Other Post-
(in thousands)	Pension Benefits				Retirement Benefits
Three Months Ended June 30, 2018	2018		2017		2018		2017
Service cost	$	3,163	$	4,093	$	28	$	47
Interest cost		4,279		4,291		161		179
Expected return on plan assets		(10,169)		(9,576)		—		—
Amortization of net loss and prior service costs		1,365		1,766		(94)		(48)
Net periodic benefit cost (reduction of cost)	$	(1,362)	$	574	$	95	$	178
					Other Post-
(in thousands)	Pension Benefits				Retirement Benefits
Six Months Ended June 30, 2018	2018		2017		2018		2017
Service cost	$	6,088	$	7,843	$	63	$	95
Interest cost		8,202		8,414		298		359
Expected return on plan assets		(19,869)		(18,326)		—		—
Amortization of net loss and prior service costs		2,691		3,201		(243)		(96)
Net periodic benefit cost (reduction of cost)	$	(2,888)	$	1,132	$	118	$	358