Retirement Plan (Net Periodic Pension Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,294	$ 1,694	$ 895
Interest cost on projected benefit obligations	787	819	638
Amortization of Prior Service Cost (Credit)	(3,482)	(3,482)	(4,296)
Amortization of net loss	0	183	0
Net periodic post-retirement credit	$ (1,401)	$ (786)	$ (2,763)