Components of Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 538	$ 510
Interest cost	879	939
Expected return on plan assets	(863)	(948)
Amortization of transition obligation	0	0
Net amortization of prior service cost	0	(2)
Net amortization of net (gain) loss	1,185	190
Net Periodic Benefit Cost	1,739	689
Post-Retirement Health Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	16	13
Interest cost	43	44
Expected return on plan assets	0	0
Amortization of transition obligation	0	0
Net amortization of prior service cost	0	0
Net amortization of net (gain) loss	0	0
Net Periodic Benefit Cost	$ 59	$ 57