Other Postretirement Benefits (Impact on Amounts Reported Due to a 1% Change in the Annual Medical Inflation Rate Issued) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Other Postretirement Benefits [Abstract]
Effect on accumulated postretirement benefit obligation, 1% increase	$ 975	$ 963
Effect on accumulated postretirement benefit obligation, 1% decrease	(824)	(825)
Effect on annual service and interest costs, 1% increase	42	40
Effect on annual service and interest costs, 1% decrease	$ (35)	$ (34)