Contract Balances and Performance Obligations - Contract Balances (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Sep. 30, 2020
Contract With Customer, Liability [Roll Forward]
Deferred revenues at September 30, 2020 *	$ 122,141
Revenue recognized that was included in the deferred revenues balance at the beginning of the period	(47,793)
Increases due to billings, excluding amounts recognized as revenue during the period	48,441
Deferred revenues at December 31, 2020 *	122,789
Deferred revenue and other liabilities, current portion	115,800	$ 115,200
Deferred revenue and other liabilities, noncurrent	$ 7,000	$ 6,900