Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year			$ 2,700
Post-Retirement Health Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year			$ 262
Service cost	$ 14	$ 16
Interest cost	46	43
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	60	59
Defined Benefit Plan, Contributions by Employer	50
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	470	538
Interest cost	932	879
Expected return on plan assets	(857)	(863)
Amortization of transition obligation	0	0
Net amortization of prior service cost	0	0
Net amortization of net (gain) loss	484	1,185
Net Periodic Benefit Cost	1,029	$ 1,739
Defined Benefit Plan, Contributions by Employer	$ 500