Retirement Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Employees' Pension Plan [Member]
Net Periodic Benefit Cost [Line Items]
Service Cost	$ 353		$ 377
Interest Cost	394		330
Expected Return on Plan Assets	(808)		(722)
Amortization of Prior Service (Credit) Cost	(20)		(11)
Amortization of Net Loss	138		86
Net Periodic Benefit Cost	57		60
Contributions to Retirement Benefits Plans	0		0
Estimated Future Contributions in the Current Fiscal Year		0
Select Executive Retirement Plan [Member]
Net Periodic Benefit Cost [Line Items]
Service Cost	3		0
Interest Cost	48		61
Expected Return on Plan Assets	0		0
Amortization of Prior Service (Credit) Cost	15		18
Amortization of Net Loss	30		23
Net Periodic Benefit Cost	96		102
Contributions to Retirement Benefits Plans	115		119
Estimated Future Contributions in the Current Fiscal Year		345
Post-Retirement Benefit Plans [Member]
Net Periodic Benefit Cost [Line Items]
Service Cost	43		53
Interest Cost	58		110
Expected Return on Plan Assets	0		0
Amortization of Prior Service (Credit) Cost	(8)		(29)
Amortization of Net Loss	24		7
Net Periodic Benefit Cost	117		141
Contributions to Retirement Benefits Plans	47		142
Estimated Future Contributions in the Current Fiscal Year		$ 141