Components of Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jul. 02, 2018	Jun. 30, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
COLA, percentage					3.00%	1.00%
Matching contribution rate			4.50%
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1,780	$ 1,905	$ 5,340	$ 5,715
Interest cost	2,129	2,111	6,387	6,333
Expected return on plan assets	(4,815)	(6,202)	(14,445)	(18,606)
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	707	2,750	2,121	8,250
Net periodic benefit cost (income)	(199)	564	(597)	1,692
RIM
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	61	59	183	177
Interest cost	111	107	333	321
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	103	113	309	339
Net periodic benefit cost (income)	275	279	825	837
Post-retirement
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	93	35	279	105
Interest cost	205	186	615	558
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	(34)	(34)	(102)	(102)
Amortization of Net loss	69	81	207	243
Net periodic benefit cost (income)	$ 333	$ 268	$ 999	$ 804