Retirement Plans (Tables)

6 Months Ended

Jun. 30, 2016

Retirement Plans [Abstract]

Components of Net Periodic Benefits Cost

					Other Post-
(in thousands)	Pension Benefits				retirement Benefits
Three Months Ended June 30, 2016	2016		2015		2016		2015
Service cost	$	3,611	$	3,382	$	45	$	22
Interest cost		4,023		4,672		203		174
Expected return on plan assets		(8,554)		(8,206)		—		—
Amortization of net loss		1,426		842		53		(40)
Net periodic benefit cost	$	506	$	690	$	301	$	156
Six Months Ended June 30, 2016
Service cost	$	6,876	$	6,745	$	74	$	72
Interest cost		9,011		9,291		409		543
Expected return on plan assets		(17,445)		(16,419)		—		—
Amortization of net loss		2,894		1,486		22		85
Net periodic benefit cost	$	1,336	$	1,103	$	505	$	700