Other Income, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Other Income and Expenses [Abstract]
Interest income	$ 61	$ 14	$ 204	$ 138
Other nonoperating income	75	108	230	266
Insurance policy (expense) income	(49)	(42)	(98)	128
Other nonoperating expense	(4)	(3)	(7)	(6)
Other income, net	$ 83	$ 77	$ 329	$ 526