Restructuring Charges - Activity Related to Restructuring Accruals (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Restructuring Reserve [Roll Forward]
Expenses	$ 49	$ 860	$ 49	$ 1,835
Workforce-related termination benefits
Restructuring Reserve [Roll Forward]
Beginning Balance	1,127	3,227	1,708	5,939
Expenses	49	860	49	1,835
Payments	(760)	(2,043)	(1,341)	(5,730)
Ending Balance	$ 416	$ 2,044	$ 416	$ 2,044