Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year					$ 1,800
Post-Retirement Health Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year					$ 247
Service cost	$ 16	$ 13	$ 47	$ 40
Interest cost	43	44	130	131
Expected return on plan assets	0	0	0	0
Amortization of transition obligation	0	0	0	0
Net amortization of prior service cost	0	0	0	0
Net amortization of net (gain) loss	0	0	0	(1)
Net Periodic Benefit Cost	59	57	177	170
Defined Benefit Plan, Contributions by Employer			161
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	538	510	1,615	1,530
Interest cost	879	939	2,637	2,817
Expected return on plan assets	(863)	(948)	(2,589)	(2,845)
Amortization of transition obligation	0	0	0	0
Net amortization of prior service cost	0	(2)	1	(7)
Net amortization of net (gain) loss	1,185	190	3,555	569
Net Periodic Benefit Cost	$ 1,739	$ 689	5,219	$ 2,064
Defined Benefit Plan, Contributions by Employer			$ 1,300