Components of Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 559	$ 1,218	$ 1,678	$ 3,654
Interest cost	846	917	2,537	2,750
Expected return on plan assets	(827)	(815)	(2,482)	(2,444)
Amortization of transition obligation	0	0	0	0
Net amortization of prior service cost	(4)	41	(12)	124
Net amortization of net (gain) loss	523	567	1,568	1,702
Net Periodic Benefit Cost	1,097	1,928	3,289	5,786
Post-Retirement Health Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	17	15	51	82
Interest cost	43	43	130	180
Expected return on plan assets	0	0	0	0
Amortization of transition obligation	15	15	44	45
Net amortization of prior service cost	0	0	0	0
Net amortization of net (gain) loss	0	0	0	0
Net Periodic Benefit Cost	$ 75	$ 73	$ 225	$ 307