Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 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	$ 41	$ 47
Interest cost	46	43	139	130
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	180	177
Defined Benefit Plan, Contributions by Employer			151
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	470	538	1,411	1,615
Interest cost	932	879	2,797	2,637
Expected return on plan assets	(857)	(863)	(2,572)	(2,589)
Amortization of transition obligation	0	0	0	0
Net amortization of prior service cost	0	0	1	1
Net amortization of net (gain) loss	484	1,185	1,451	3,555
Net Periodic Benefit Cost	$ 1,029	$ 1,739	3,088	$ 5,219
Defined Benefit Plan, Contributions by Employer			$ 2,100