Revenue from Contracts with Customers - Capitalized Contract Acquisition Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Capitalized Contract Acquisition Costs [Abstract]
Balance, beginning of year	$ 59,446	$ 0
Capitalized Contract Cost, Cumulative Catch-up Adjustment to Revenue, Change in Estimate of Transaction Price	0	54,608
Capitalized Contract Cost, Deferred Acquisition Costs	43,557	33,925
Capitalized Contract Cost, Amortization	(32,607)	(29,087)
Balance, end of year	$ 70,396	$ 59,446