Defined Benefit Pension Plans Schedule of Net Periodic Pension Benefit Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan [Abstract]
Service cost	$ 3,968	$ 3,472	$ 4,572
Interest cost	2,264	2,573	2,380
Expected Return on Plan Assets	(594)	(540)	(502)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	62	58	59
Amortization of actuarial net (gains) loss	2,308	1,351	1,979
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	(2)	1,343	375
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment	(586)	0	46
Defined Benefit Plan, Other Cost (Credit)	0	(3)	(1)
Net Periodic Benefit Cost	$ 7,420	$ 8,254	$ 8,908