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Acquisitions - Additional Information (Detail)
$ in Thousands
12 Months Ended
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Business
Business Acquisition [Line Items]    
Business acquisition   $ 355,142
Number of businesses acquired | Business   3
TTS Wireless [Member]    
Business Acquisition [Line Items]    
Business acquisition $ 50,000