Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 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	$ 27	$ 32
Interest cost	46	43	93	87
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	0
Net Periodic Benefit Cost	60	59	120	119
Defined Benefit Plan, Contributions by Employer			99
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	470	538	941	1,076
Interest cost	932	879	1,865	1,758
Expected return on plan assets	(857)	(863)	(1,715)	(1,726)
Amortization of transition obligation	0	0	0	0
Net amortization of prior service cost	0	0	0	0
Net amortization of net (gain) loss	484	1,185	967	2,370
Net Periodic Benefit Cost	$ 1,029	$ 1,739	2,058	$ 3,478
Defined Benefit Plan, Contributions by Employer			$ 1,200