Share-Based Compensation (Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Intrinsic value, exercises in period	$ 26,051
Options
Outstanding at beginning of the period (shares)	8,619,000
Granted (shares)	800,000
Exercised (shares)	(1,711,000)
Cancelled (shares)	(5,000)
Forfeited (shares)	(106,000)
Outstanding at end of the period (shares)	7,597,000
Options exercisable (shares)	5,294,000
Options vested and expected to vest (shares)	7,521,000
Weighted Average Exercise Price/Share
Weighted average exercise price, outstanding, beginning balance (in dollars per share)	$ 8.15
Weighted average exercise price, granted (in dollars per share)	23.52
Weighted average exercise price, exercised (in dollars per share)	5.61
Weighted average exercise price, cancelled (in dollars per share)	20.50
Weighted average exercise price, forfeited (in dollars per share)	15.05
Weighted average exercise price, outstanding, ending balance (in dollars per share)	10.24
Weighted average exercise price, exercisable (in dollars per share)	6.92
Weighted average exercise price, options vested and expected to vest (in dollars per share)	$ 10.13
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term, outstanding	6 years 2 months 12 days	6 years 3 months 18 days
Weighted average contractual term, exercisable	5 years 1 month 6 days
Weighted average remaining contractual term, options vested and expected to vest	6 years 2 months 12 days
Intrinsic value, outstanding	$ 69,871		$ 80,826
Intrinsic value, exercisable	63,047
Intrinsic value, options vested and expected to vest	$ 69,763