Retirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Employees' Pension Plan [Member]
Net Periodic Benefit Cost [Line Items]
Service Cost	$ 376	$ 353	$ 1,127	$ 1,058
Interest Cost	420	402	1,262	1,203
Expected Return on Plan Assets	(828)	(808)	(2,483)	(2,423)
Amortization of Prior Service (Credit) Cost	(14)	(21)	(42)	(62)
Amortization of Net Loss	140	139	419	417
Net Periodic Benefit Cost	94	65	283	193
Contributions to Retirement Benefits Plans	0	3,000	0	3,000
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year			0
Select Executive Retirement Plan [Member]
Net Periodic Benefit Cost [Line Items]
Service Cost	8	3	24	8
Interest Cost	56	61	163	182
Expected Return on Plan Assets	0	0	0	0
Amortization of Prior Service (Credit) Cost	14	15	43	44
Amortization of Net Loss	28	30	84	91
Net Periodic Benefit Cost	106	109	314	325
Contributions to Retirement Benefits Plans	131	70	350	344
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year			117
Post-Retirement Benefit Plans [Member]
Net Periodic Benefit Cost [Line Items]
Service Cost	63	43	188	130
Interest Cost	83	144	178	361
Expected Return on Plan Assets	0	0	0	0
Amortization of Prior Service (Credit) Cost	(3)	(8)	(8)	(23)
Amortization of Net Loss	0	24	0	71
Net Periodic Benefit Cost	143	203	358	539
Contributions to Retirement Benefits Plans	$ 47	$ 106	197	$ 231
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year			$ 66