Fair Value of Financial Instruments - Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017
Level 2
Debt instruments
Fair Value	$ 201,100	$ 202,100
Carrying value	200,000	200,000
Assets and liabilities measured at fair value
Assets
Cash equivalents	5,001	8,501
Current derivative assets	2,416	2,591
Noncurrent derivative assets	443	1,128
Total assets measured at fair value	7,860	12,220
Liabilities
Current derivative liabilities	2,601	3,456
Noncurrent derivative liabilities	443	1,128
Total liabilities measured at fair value	6,809	9,801
Assets and liabilities measured at fair value | Deltenna
Liabilities
Contingent consideration to seller	1,361	1,376
Assets and liabilities measured at fair value | H4 Global
Liabilities
Contingent consideration to seller	704	591
Assets and liabilities measured at fair value | Contract extensions | TeraLogics
Liabilities
Contingent consideration to seller	900	800
Assets and liabilities measured at fair value | Revenue Targets | TeraLogics
Liabilities
Contingent consideration to seller	800	2,450
Assets and liabilities measured at fair value | Level 1
Assets
Cash equivalents	5,001	8,501
Total assets measured at fair value	5,001	8,501
Assets and liabilities measured at fair value | Level 2
Assets
Current derivative assets	2,416	2,591
Noncurrent derivative assets	443	1,128
Total assets measured at fair value	2,859	3,719
Liabilities
Current derivative liabilities	2,601	3,456
Noncurrent derivative liabilities	443	1,128
Total liabilities measured at fair value	3,044	4,584
Assets and liabilities measured at fair value | Level 3
Liabilities
Total liabilities measured at fair value	3,765	5,217
Assets and liabilities measured at fair value | Level 3 | Deltenna
Liabilities
Contingent consideration to seller	1,361	1,376
Assets and liabilities measured at fair value | Level 3 | H4 Global
Liabilities
Contingent consideration to seller	704	591
Assets and liabilities measured at fair value | Level 3 | Contract extensions | TeraLogics
Liabilities
Contingent consideration to seller	900	800
Assets and liabilities measured at fair value | Level 3 | Revenue Targets | TeraLogics
Liabilities
Contingent consideration to seller	$ 800	$ 2,450