Defined Benefit Pension Plans Level 3 Plan Asset Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 12,834	$ 10,215	$ 9,662
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	786	604
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	984	(29)
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	12,045	9,432	8,867
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	780	640
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchases, Sales, and Settlements	9	(30)
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Assets Transferred into (out of) Level 3	833	0
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	991	(45)
Guaranteed Insurance Contract, Type of Benefit [Domain]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	8,384	7,011
Guaranteed Insurance Contract, Type of Benefit [Domain] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	8,384	7,011	7,089
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	257	235
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchases, Sales, and Settlements	102	54
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Assets Transferred into (out of) Level 3	0	0
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	1,014	(367)
Securities (Assets) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3,661	2,421
Securities (Assets) [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3,661	2,421	$ 1,778
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	523	405
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchases, Sales, and Settlements	(93)	(84)
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Assets Transferred into (out of) Level 3	833	0
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	$ (23)	$ 322