Business Combinations - Narrative (Details) - USD ($) $ in Millions			3 Months Ended	9 Months Ended
	Jan. 24, 2020	May 08, 2019	Jun. 30, 2020	Jun. 30, 2020
Shape Security, Inc.
Business Acquisition [Line Items]
Total purchase price	$ 1,000.0
Transaction costs	$ 23.2
Identifiable intangible assets useful life	6 years 6 months
Shape Security, Inc. | General and Administrative Expense
Business Acquisition [Line Items]
Business combination, acquisition related costs				$ 15.3
F5 Networks Acquisition of Nginx
Business Acquisition [Line Items]
Total purchase price		$ 643.2
Transaction costs		$ 19.0
Identifiable intangible assets useful life		8 years 1 month 6 days
Goodwill, Other Increase (Decrease)			$ 6.0
Tax deductible goodwill		$ 490.3
F5 Networks Acquisition of Nginx | General and Administrative Expense
Business Acquisition [Line Items]
Transaction costs		$ 1.0
Developed Technology Rights | Shape Security, Inc.
Business Acquisition [Line Items]
Identifiable intangible assets useful life	7 years
Developed Technology Rights | F5 Networks Acquisition of Nginx
Business Acquisition [Line Items]
Identifiable intangible assets useful life		7 years
Customer Relationships | Shape Security, Inc.
Business Acquisition [Line Items]
Identifiable intangible assets useful life	4 years
Customer Relationships | F5 Networks Acquisition of Nginx
Business Acquisition [Line Items]
Identifiable intangible assets useful life		15 years
Trade Names | Shape Security, Inc.
Business Acquisition [Line Items]
Identifiable intangible assets useful life	5 years
Trade Names | F5 Networks Acquisition of Nginx
Business Acquisition [Line Items]
Identifiable intangible assets useful life		7 years