Revenue from Contracts with Customers - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Change in Contract with Customer, Asset [Roll Forward]
Beginning Balance	$ 200,472	$ 132,492
Revenue recognized during period but not yet billed	18,316	3,407
Contract asset additions	55,834	12,930
Contract assets reclassified to accounts receivable	(28,818)	(13,584)
Ending Balance	245,804	135,245
Change in Contract with Customer, Liability [Roll Forward]
Beginning Balance	1,272,632	1,198,116
Amounts billed but not recognized as revenues	421,918	346,132
Revenues recognized related to the opening balance of deferred revenue	(335,725)	(306,275)
Ending Balance	$ 1,358,825	$ 1,237,973