Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Goodwill And Intangible Assets Disclosure [Line Items]
Cost, Depreciation and Amortization			$ 36,800	$ 50,900	$ 57,900
Document Fiscal Year Focus			2019
Other Asset Impairment Charges			$ 0	10,550	16,351
Goodwill	$ 3,247,105		3,243,464	3,247,105	3,332,816
Goodwill, Transfers				0
Intangible assets	450,001		356,932	450,001
Issuance of common stock in connection with business and asset acquisitions					16,347
Goodwill, Impairment Loss				141,781
Impairment of goodwill and other intangible assets			0	170,941	0
Intangible Assets Amortization Expense			66,730	73,997	92,839
Technology and patents
Goodwill And Intangible Assets Disclosure [Line Items]
Intangible assets	122,960		97,481	122,960
Trade names, trademarks and other
Goodwill And Intangible Assets Disclosure [Line Items]
Intangible assets	10,475		4,410	10,475
Customer Relationships
Goodwill And Intangible Assets Disclosure [Line Items]
Intangible assets	316,566		$ 255,041	316,566
SRS [Member]
Goodwill And Intangible Assets Disclosure [Line Items]
Other Asset Impairment Charges	900
Goodwill, Impairment Loss	3,400
Impairment of goodwill and other intangible assets	25,100
SRS [Member] | Technology and patents
Goodwill And Intangible Assets Disclosure [Line Items]
Impairment of Intangible Assets (Excluding Goodwill)	7,900
SRS [Member] | Customer Relationships
Goodwill And Intangible Assets Disclosure [Line Items]
Impairment of Intangible Assets (Excluding Goodwill)	12,900
Mobile Reporting Unit [Member]
Goodwill And Intangible Assets Disclosure [Line Items]
Other Asset Impairment Charges	6,200
Goodwill	0	$ 36,000		0	$ 1,241,010
Goodwill, Transfers				(1,249,051)
Goodwill, Impairment Loss	400	35,100		$ 0
Impairment of goodwill and other intangible assets	15,000
Mobile Reporting Unit [Member] | Technology and patents
Goodwill And Intangible Assets Disclosure [Line Items]
Impairment of Intangible Assets (Excluding Goodwill)	800
Mobile Reporting Unit [Member] | Customer Relationships
Goodwill And Intangible Assets Disclosure [Line Items]
Impairment of Intangible Assets (Excluding Goodwill)	$ 7,600
Dragon TV [Member]
Goodwill And Intangible Assets Disclosure [Line Items]
Goodwill		$ 12,000