Retirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Employees' Pension Plan
Net Periodic Benefit Cost [Line Items]
Service Cost	$ 350	$ 376
Interest Cost	350	420
Expected Return on Plan Assets	(800)	(826)
Amortization of Prior Service (Credit) Cost	(14)	(14)
Amortization of Net Loss	148	138
Net Periodic Benefit Cost	34	94
Plan Contributions During the Period	0	0
Select Executive Retirement Plan
Net Periodic Benefit Cost [Line Items]
Service Cost	10	8
Interest Cost	50	58
Expected Return on Plan Assets	0	0
Amortization of Prior Service (Credit) Cost	14	14
Amortization of Net Loss	30	28
Net Periodic Benefit Cost	104	108
Plan Contributions During the Period	113	107
Post-Retirement Benefit Plans
Net Periodic Benefit Cost [Line Items]
Service Cost	37	62
Interest Cost	86	80
Expected Return on Plan Assets	0	0
Amortization of Prior Service (Credit) Cost	(3)	(3)
Amortization of Net Loss	0	0
Net Periodic Benefit Cost	120	139
Plan Contributions During the Period	$ 53	$ 78