Retirement Plans - Accumulated Other Comprehensive loss (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Loss
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 0
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year	$ 5,270
Amortization period	17 years
Post-Retirement Life Insurance Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 4,595	$ 5,134
Accumulated Other Comprehensive Loss
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year	$ 0
Amortization period	4 years
Post-Retirement Life Insurance Plan | Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss)
Accumulated Other Comprehensive Loss
Beginning balance	$ (379)	(560)
Amortization of retirement benefits, net of tax	36	64
Net actuarial (loss) gain	(418)	117
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(88)
Ending balance	(849)	(379)
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	205,319	228,934
Accumulated Other Comprehensive Loss
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	17,560
Domestic Plan [Member] | Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss)
Accumulated Other Comprehensive Loss
Beginning balance	75,740	89,763
Amortization of retirement benefits, net of tax	(4,538)	(3,685)
Settlements	19,083	(8,585)
Net actuarial (loss) gain	(12,351)	(1,753)
Foreign exchange impact	0	0
Ending balance	95,494	75,740
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	1,936	2,535
Foreign Plan [Member] | Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss)
Accumulated Other Comprehensive Loss
Beginning balance	1,898	1,743
Amortization of retirement benefits, net of tax	(126)	10
Settlements	0	0
Net actuarial (loss) gain	196	2
Foreign exchange impact	(52)	143
Ending balance	$ 1,916	$ 1,898