Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Retirement Benefits [Abstract]
Years of employment benefits are based upon			5 years
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1,746	$ 1,780	$ 4,748	$ 5,340
Interest cost	2,090	2,129	6,478	6,387
Expected return on plan assets	(5,802)	(4,815)	(15,256)	(14,445)
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	770	707	2,300	2,121
Net periodic (income) benefit cost	(1,196)	(199)	(1,730)	(597)
RIM Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	53	61	159	183
Interest cost	116	111	348	333
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	61	103	183	309
Net periodic (income) benefit cost	230	275	690	825
Post-retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	172	93	516	279
Interest cost	321	205	963	615
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	14	(34)	42	(102)
Amortization of Net loss	99	69	297	207
Net periodic (income) benefit cost	$ 606	$ 333	$ 1,818	$ 999