Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Unrealized gains (losses)	$ (5,671)
Amounts reclassified from AOCI	174
Accumulated Other Comprehensive Income
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	24,454
Ending Balance	18,957
Derivative instruments
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	0
Unrealized gains (losses)	168
Amounts reclassified from AOCI	88
Ending Balance	256
Pension, Postretirement and Other Postemployment Benefits
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	24,067
Unrealized gains (losses)	(5,784)
Amounts reclassified from AOCI	418
Ending Balance	18,701
Available-for-sale securities
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	387
Unrealized gains (losses)	(55)
Amounts reclassified from AOCI	(332)
Ending Balance	$ 0