Post-Retirement Health Care (Components of Net Periodic Post-retirement Benefit Cost) (Details) - Other postretirement plans $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 742
Interest cost	825
Amortization of net (gain)/loss	25
Net periodic post-retirement benefit cost/(income)	$ 1,592