Supporting Financial Information - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Interest expense									$ (800)	$ (883)
Amortization of debt financing costs as interest expense									(275)	(268)
Change in fair value of derivative financial instruments									0	(102)
Other income (expense), net									(41)	25
Interest expense, net	$ (315)	$ (262)	$ (261)	$ (278)	$ (340)	$ (269)	$ (255)	$ (364)	$ (1,116)	$ (1,228)