Retirement Plans, Amounts Recognized in Accumulated Other Comprehensive Income Table (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Retirement Account Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	$ (303)	$ (295)
Net actuarial loss	50,238	24,926
Amount not yet recognized in net periodic benefit cost, but recognized in accumulated other comprehensive (income) loss	49,935	24,631
Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	(588)	(531)
Net actuarial loss	(17)	205
Amount not yet recognized in net periodic benefit cost, but recognized in accumulated other comprehensive (income) loss	$ (605)	$ (326)

Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (i-k)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant